We consider replenishment mandatory. What I mean by that is we assume that you have replenishment available to your raid.And later:
...we don't want it to feel optional...And finally:
...we assume you have replenishment just like we assume you have a tank.Right now, replenishment is available via talents to shadow priests, retribution paladins and survival hunters. If you ask me, that makes it far too specialised for you to be able to rely on having it, at least in 10 man raids. Blizzard, it would seem, agrees, because in 3.1 replenishment will become available additionally to frost mages and destruction warlocks. It may not have passed you by that these are rather underwhelming talent trees right now, so we can assume this gift is intended to boost their appeal to raiders.
Blizzard is going to extraordinary lengths to ensure an abundance of replenishment because, by their own design, the buff is mandatory. After having gone to extraordinary lengths not-so-long ago to design a raid buff system that ensured no buffs were... mandatory.
They are designing encounters around the assumption that every mana-using class will have a near-constant mana regeneration effect on them — at exactly the same time they are changing how mana regeneration works because some classes and specs had simply no reason to manage mana at all.
At best, this is a lazy, over-simplified bandage on a far-more variable problem. Every mana-using class already has personal mana-management tools available to it. They work in different ways and are designed to fit with the lore and stylistic design of the individual classes. This is a system I can understand and support, because it ensures each class has control over their own resources and are able to manage them accordingly. If you start designing around external (raid-wide) factors you are essentially saying this is not enough. But of course we know, from the problem with healer mana, that it often is enough. So this is very clearly not a one-size-fits all issue, despite what Blizzard would have us believe.
In fact, with replenishment, Blizzard seems destined to repeat old mistakes. Shadow priest stacking in BC drove designers to pressure healers in ways other than longevity, because it was simply impossible to engineer them to run out of mana. They consequently changed vampiric touch to prevent that situation from continuing.
But with replenishment we see the same problem — sure, it's on a much smaller scale, and yes, it's spread across several classes instead of just one, but the design flaw is essentially identical: mana regeneration has become a non-issue to healers (again) because of the power and availability of group regeneration buffs (again).
They did the right think in tackling vampiric touch, even if I don't like the end result. But this time, they've missed the mark — the problem is not with healer regeneration, it is with the range and power of the raid-wide buffs they receive that boost their regeneration to such trivial levels. Why hurt base regeneration when external buffs remain so powerful? Why make sweeping changes to mana regeneration which you have to work around for other classes, when each class and talent tree needs to be considered individually?
Admittedly, this is not just a replenishment issue. Blessing of wisdom and mana spring are both powerful raid buffs in their own right. But these provide fixed mana returns, so do not scale so powerfully, nor, as far as we know, are they considered mandatory.
If Blizzard is serious about making raids accessible to all specs and all classes, and removing the need to stack certain combinations, they need to look again at replenishment, which is the true cause of this issue, not get distracted by the symptoms.