With the removal of spirit (often a significant source of passive regeneration) from non-healing casters, they're going to need different methods for replenishing their supply. Magi have Evocation and Mana Gems; warlocks have Life Tap; balance druids currently sustain themselves entirely on the refunding mana on crit aspect of Moonkin Form. Our primary mana return method is highly flawed, however, and cannot be supported within a new expansion. That's right: Moonkin Form is a terrible mechanic, at least in light of its being a primary source of mana regeneration.
I must be crazy, right? Moonkin Form's refunding mana on crits is currently one of the single best mana return systems that we have in place in the game, once you get into ICC. That is the issue, though: It is only viable in ICC. Way back in Naxx, balance druids could not rely entirely upon Moonkin Form for their mana regeneration; we had to either use our own Innervates or spec into Intensity in order to be able to sustain ourselves. It wasn't until ICC that the mechanic became grossly overpowered. It isn't so much the massive amounts of additional crit that we have gained, although that is a major factor as well, as much as it is that we now have such ridiculously huge mana pools. We have finally reached the point where nearly every single crit that we make doesn't just refund us mana, but it more than covers the cost of the spell used and replenishes it. A balance druid can receive Rebirth in the middle of an encounter and by the end of the encounter have near 100% mana once again.
Why Moonkin Form mana return is not sustainable
As I said, the Moonkin Form mechanic is highly flawed in such a way that it simply cannot be used as our primary source of mana regeneration. The reasoning behind this is the same reasoning the mechanic is currently so powerful in ICC content: The scaling factor of the ability is completely out of whack. Do not misunderstand me, there is nothing wrong with a scaling mana return system; in fact, all mana return systems should scale to a degree. The Moonkin Form mechanic, however, simply doesn't scale in a way that is viable to balance a class around. In the lower end of gearing, it simply cannot return enough mana to be used on its own, while at higher levels of gearing, it becomes all that a player needs. Unless the mechanic no longer scales as well as it currently does, it isn't possible to balance around both extremes.
The mechanic itself is simply too strong as it stands in ICC gear; while gear scaling issues should change, this means little for the mechanic. If this mechanic is going to exist, then one of the scaling portions is going to have to be removed. The only viable method that I can think of for removing scaling from the mechanic is to either have it return a percentage of mana spent on the spell or to return a flat value of mana. In short, the amount of mana gained per crit can never change with gear.
All of this may seem odd; the mana on crit mechanic is so beautiful, so amazing and I love it more than I could possibly say, so why does it not work? Forget the scaling factor, forget the imbalance between gearing levels; the true flaw in the mechanic is that it isn't a controllable return system. Moonkin Form is not Innervate, it is not Evocation, it is not Life Tap; a balance druid cannot choose when to gain mana back, and it requires the expenditure of mana in order to get mana back. Starting at a near zero mana level, this is terrible. If a balance druid does not have any mana, then they have no means of getting mana back. Not to mention that if the mana return isn't higher than the spell cost, then the druid is still going to run out of mana at some point unless he has another viable method to refund mana. It's a flawed catch-22.
Gaining mana needs to be an active choice. Passive mana regeneration is a nice perk, but it should never be the primary system if the design intent is for DPS casters to only marginally worry about mana. Passive forms of mana regeneration should exist not to wholly sustain a caster, but merely to supplement him. As passive mana regeneration increases, less reliance can then be placed on active regeneration, similar to how the mage system works. Mages currently have multiple passive mana regeneration techniques that exist not to sustain their mana but to help them rely less on their active mana regeneration abilities. Balance druids do not have this, and we need it.
Moonkin Form mana return in PvP
The way things stand now, the Moonkin Form mana return mechanic is downright unusable in PvP. With the lowered crit rates of PvP players, the lower mana pools and the way in which resilience functions, it is impossible for a balance druid to sustain himself via Moonkin Form in PvP. A portion of this is being addressed in the way in which resilience is being changed for Cataclysm.
Resilience - This will only affect damage done by players and critical damage done by players. It will not impact crit chance, mana drains, or other such effects.
Regardless of the resilience change, this does absolutely nothing to address the sustainability of the mechanic in PvP; it is still subject to the same catch-22 of needing to spend mana in order to gain mana. In PvE, such a system may not be as terrible, since there are very limited times when a player is going to find themselves without mana; however, the same is not true for PvP. Mana drains, the need to shift constantly and using a wide variety of abilities which are not affected by the mechanic (such as CC and healing) will all drain the player's mana far faster than they could ever replenish it.
Balance druids do not need to have infinite mana in PvP; in fact, no caster should have infinite mana in PvP, but they should have a viable method of getting some mana back. The hunter's Aspect of the Viper
is a very clean system for such a thing. Using Aspect of the Viper will get the hunter back to full mana in a decent amount of time, yet it comes with a cost of vastly reduced damage for the duration. Having to pay a price in order to refund mana is a nicely balanced system, especially for a class that has the ability to heal. To that end, any active form of mana regeneration that would mirror Aspect of the Viper would have to do two things for any healing-capable class. First, it would have to reduce their damage as it currently does with hunters; the point of regaining mana is so that you can unload higher amounts of damage, and you should not be able to perpetually put out high amounts of pressure while retaining infinite mana at the same time. Second, the mechanic would also have to limit healing in some form, either by locking out healing abilities or reducing their effects similar to Divine Plea
. Again, the point is not to allow the player to do whatever they want without any cost associated with their actions; it is merely to never allow the player to have to sit there unable to do anything.