The problem with mana
Mana creates a game mechanic where players must make choices. They bargain with the game using a kind of currency. You can save up and splurge later, or blow your wad now, investing in the hope that your debts won't catch up to you. For healers, this kind of bargaining makes a lot of sense. Healers are in the business of risk management. Our heals mitigate risk of player deaths and wipes. But the more healing we throw into the encounter, the less value each additional heal has. At a point, the group will be so saturated with heals that throwing more would have little to no benefit. So there are two competing forces: the need to heal and the need to not exhaust our mana. As we heal more and more, the value of additional healing declines, and the need to conserve mana balances it out. An equilibrium is reached, and the player's skill is in finding and maintaining that equilibrium. Or at least so it should be. In the current WoW content, healer's rarely exhaust their mana. And Blizzard is making changes to the speed at which mana regenerates to try and re-introduce this equilibrium and aspect of player skill into the healing game.
But none of this really makes sense for damage dealers, who convert their mana into offensive spells. For a DPS class, adding more DPS always has value. In most cases, the value never even changes. DPS is DPS is DPS. So there's never any equilibrium point at which it makes sense to conserve mana. No interesting choices are presented to the player. They simply run out of mana when they run out and then they get to sit there and wait. Most classes have abilities that return mana that are on longish cooldowns that players need to use at times they decide are most useful.
It occurs to me that the current model of DPS mana as a resource in WoW is a little like auto racing. Mana is the fuel. I don't actually know too much about F1 racing, but it seems like there isn't really a concept of conserving fuel. More speed is always better. The decisions that a driver makes as it relates to fuel seem to mostly be when to take pitstops. Drivers try not to force themselves into taking pitstops at critical points in the race, or when they would not get the full benefit of the pitstop. DPS mana classes, especially mages, are much like that. You have a series of mana-returning cooldowns and you have to pick the best time to use them.
But it's not really a very fun model, any more than watching pitstops during F1 races are fun for fans. It seems a more interesting model is the 'fuel' used by a cyclist or runner. Here there is a concept of conservation, because the human body can burst out extra effort but only for a short time, and doing so exhausts you. So you use your periods of burst wisely, and if they have reserves of energy available, you generally see athletes go into 'burn mode' as they approach the finish line. Periods of burst are more interesting and fun than periods of stopping to recover.
This was actually the basic design of the arcane mage during TBC. They could choose to do more damage but only by spending an inordinately greater amount of mana. They couldn't sustain their high-damage mode for very long. This kind of mechanic is interesting but leads to a few problems. Burst damage is hard to balance in PVP, especially if certain classes have better burst capability. Blizzard balanced the arcane mage by having the burst mode require an uninterrupted series of casts to 'ramp up,' something that is not practical to try in PVP. Also, because of innervate, groups could use a brigade of druids to arrange to keep one mage in constant burn mode, something that is very much contrary to the current raid make-up philosophy. Apparently Blizzard decided it wasn't worth trying to balance it because they heavily nerfed the arcane mage's 'burn' mechanic for WotLK, although they've done a pretty good job of preserving the flavour of it.
Of course, there are other ways to make mana conservation a strategic choice. For example, DPS can have different values at different times. In any multi-phase or multi-mob fight it often pays to pump out more damage at one time or another. The simplest and most common example is bosses that have a "soft enrage" at low health. If the last 10% of the fight is the most dangerous, the DPS should make sure that they have enough mana to blow through it without slowing down, even if it means they need to hold back a bit before then. But for damage dealers though, it's never a fun game choice to 'hold back'. Damage is what they're there to do, and doing less than the most possible is not a fun choice to make, even if it's the right one. So even though the fight might favour burst damage during part of it, mana conservation never really comes into play.
Other options are to give the player other things they can "purchase" with their "currency". The warlock design is good example of this. They can buy mana at the cost of health. So for them mana is essentially a currency they can spend on damage or survivability. This works especially well in PVP where the choice can be very difficult. In most PVE encounters though, it's rarely a real choice. You give up health for mana when you need the mana. You could try to extend that mechanic by having very costly shields that a player could choose to use to, trading damage for survivability. Mages already have this with Mana Shield. And I'll bet no mage ever uses it outside of extreme cases like being focused by Fel Rage in the Bloodboil fight.
Another method is to have the currency be more like an allowance than a fixed starting amount. If players only get so much mana per second, they can choose to spend it in different ways or save it up for later. This is basically the design of "mana" for melee classes who gain resources (energy, rage, or runic power) at much faster rates than mana-users and make decisions constantly about how best to spend it. But I think Blizzard wants to preserve the distinction of the caster classes resource system. They have a "full tank of fuel" at the start of the fight and have to choose how to use it best without running out. I think the arcane mage has been the best attempt at it so far. I would take that idea and run with it. Give every caster a 'burn mode' so that you don't unbalance things by having certain classes excel at shorter fights or burst damage. They don't have to be the exact same thing. Here are some ideas for ways to extend the idea of the 'burn' mechanic that should not overly unbalance PVP:
A mage mana dump. To balance this, Icy Veins or shields should not count as preventing "interruption". This makes it about as unusable in PVP as pyro without the PoM, especially if the beam is really obvious (which would be cool for PVE.)
Here's one for the Shadow Priest. No real PVP application but handy for getting rid of excess mana at the end of a fight. Give it a dark, sinister version of the Angel of Redemption graphic!
Who doesn't love Moonfire spam? It's already kind of a mana dump. It just doesn't do enough damage to ever be worth it. The idea here is to make it a useful ramp-up to doing some serious Starfire spam. It just costs a lot of time and mana to get it up to that point. It's kind of a moonkin version of the old Arcane mana dump. It might not even need the target health limitation to make unusable in PVP.
One for the elemental shaman. I like the idea of setting your own totems alight with sparks and fire. Since totems are trivially easy to kill, and the graphic should be really obvious (and cool!) there's almost no reason to try this in PVP. (Should probably be unusable on Stoneclaw Totem.)
Note that the warlock can't really have a mana dump due to how their resource system works. They already have a working mana model though and don't need any help. I think these all sound pretty fun and would make mana an interesting resource to manage, provided fights are neither too short nor too long. You could burst out mana during critical stages in the fight, which a lot of cases would just be the home stretch. Like a great marathon finish, you'd come sprinting to the finish line, and if you timed it right, be literally exhausted of all your energy when the fight is won.
But none of this really makes sense for damage dealers, who convert their mana into offensive spells. For a DPS class, adding more DPS always has value. In most cases, the value never even changes. DPS is DPS is DPS. So there's never any equilibrium point at which it makes sense to conserve mana. No interesting choices are presented to the player. They simply run out of mana when they run out and then they get to sit there and wait. Most classes have abilities that return mana that are on longish cooldowns that players need to use at times they decide are most useful.
It occurs to me that the current model of DPS mana as a resource in WoW is a little like auto racing. Mana is the fuel. I don't actually know too much about F1 racing, but it seems like there isn't really a concept of conserving fuel. More speed is always better. The decisions that a driver makes as it relates to fuel seem to mostly be when to take pitstops. Drivers try not to force themselves into taking pitstops at critical points in the race, or when they would not get the full benefit of the pitstop. DPS mana classes, especially mages, are much like that. You have a series of mana-returning cooldowns and you have to pick the best time to use them.
But it's not really a very fun model, any more than watching pitstops during F1 races are fun for fans. It seems a more interesting model is the 'fuel' used by a cyclist or runner. Here there is a concept of conservation, because the human body can burst out extra effort but only for a short time, and doing so exhausts you. So you use your periods of burst wisely, and if they have reserves of energy available, you generally see athletes go into 'burn mode' as they approach the finish line. Periods of burst are more interesting and fun than periods of stopping to recover.
This was actually the basic design of the arcane mage during TBC. They could choose to do more damage but only by spending an inordinately greater amount of mana. They couldn't sustain their high-damage mode for very long. This kind of mechanic is interesting but leads to a few problems. Burst damage is hard to balance in PVP, especially if certain classes have better burst capability. Blizzard balanced the arcane mage by having the burst mode require an uninterrupted series of casts to 'ramp up,' something that is not practical to try in PVP. Also, because of innervate, groups could use a brigade of druids to arrange to keep one mage in constant burn mode, something that is very much contrary to the current raid make-up philosophy. Apparently Blizzard decided it wasn't worth trying to balance it because they heavily nerfed the arcane mage's 'burn' mechanic for WotLK, although they've done a pretty good job of preserving the flavour of it.
Of course, there are other ways to make mana conservation a strategic choice. For example, DPS can have different values at different times. In any multi-phase or multi-mob fight it often pays to pump out more damage at one time or another. The simplest and most common example is bosses that have a "soft enrage" at low health. If the last 10% of the fight is the most dangerous, the DPS should make sure that they have enough mana to blow through it without slowing down, even if it means they need to hold back a bit before then. But for damage dealers though, it's never a fun game choice to 'hold back'. Damage is what they're there to do, and doing less than the most possible is not a fun choice to make, even if it's the right one. So even though the fight might favour burst damage during part of it, mana conservation never really comes into play.
Other options are to give the player other things they can "purchase" with their "currency". The warlock design is good example of this. They can buy mana at the cost of health. So for them mana is essentially a currency they can spend on damage or survivability. This works especially well in PVP where the choice can be very difficult. In most PVE encounters though, it's rarely a real choice. You give up health for mana when you need the mana. You could try to extend that mechanic by having very costly shields that a player could choose to use to, trading damage for survivability. Mages already have this with Mana Shield. And I'll bet no mage ever uses it outside of extreme cases like being focused by Fel Rage in the Bloodboil fight.
Another method is to have the currency be more like an allowance than a fixed starting amount. If players only get so much mana per second, they can choose to spend it in different ways or save it up for later. This is basically the design of "mana" for melee classes who gain resources (energy, rage, or runic power) at much faster rates than mana-users and make decisions constantly about how best to spend it. But I think Blizzard wants to preserve the distinction of the caster classes resource system. They have a "full tank of fuel" at the start of the fight and have to choose how to use it best without running out. I think the arcane mage has been the best attempt at it so far. I would take that idea and run with it. Give every caster a 'burn mode' so that you don't unbalance things by having certain classes excel at shorter fights or burst damage. They don't have to be the exact same thing. Here are some ideas for ways to extend the idea of the 'burn' mechanic that should not overly unbalance PVP:
Mana Blast - 60% base mana - fires a beam of pure mana at the target which ignites after 6 seconds for 3600 damage. Caster must channel the spell without interruption.
A mage mana dump. To balance this, Icy Veins or shields should not count as preventing "interruption". This makes it about as unusable in PVP as pyro without the PoM, especially if the beam is really obvious (which would be cool for PVE.)
Angel of Death - 150% base mana - 3 second cast - You become an angel of death, dealing 50% additional damage to targets below 35% health. Lasts for 60 seconds. Can only be cast in combat.
Here's one for the Shadow Priest. No real PVP application but handy for getting rid of excess mana at the end of a fight. Give it a dark, sinister version of the Angel of Redemption graphic!
Owlkin Rage - Your Moonfire spell increases your haste by 5% when used against targets with less than 50% health. Stacks up to 10 times. Lasts 60 seconds.
Who doesn't love Moonfire spam? It's already kind of a mana dump. It just doesn't do enough damage to ever be worth it. The idea here is to make it a useful ramp-up to doing some serious Starfire spam. It just costs a lot of time and mana to get it up to that point. It's kind of a moonkin version of the old Arcane mana dump. It might not even need the target health limitation to make unusable in PVP.
Totemic Detonation - 100% base mana - Targets one of your totems for detonation. After 15 seconds your totem deals 5000 damage to your current target in Fire, Frost, Nature, or Arcane damage as appropriate to the totem's school.
One for the elemental shaman. I like the idea of setting your own totems alight with sparks and fire. Since totems are trivially easy to kill, and the graphic should be really obvious (and cool!) there's almost no reason to try this in PVP. (Should probably be unusable on Stoneclaw Totem.)
Note that the warlock can't really have a mana dump due to how their resource system works. They already have a working mana model though and don't need any help. I think these all sound pretty fun and would make mana an interesting resource to manage, provided fights are neither too short nor too long. You could burst out mana during critical stages in the fight, which a lot of cases would just be the home stretch. Like a great marathon finish, you'd come sprinting to the finish line, and if you timed it right, be literally exhausted of all your energy when the fight is won.