We're complaining about lightwell - but I think we're missing the (potentially) huge buff it's getting. If we're going to be mana starved, we face the following situation: Heal up all the dps that just took damage for a lot of mana, or spend a little on a lightwell and remind them "click the thing or die, because I can't afford to heal you". While nobody likes making the dps stop dpsing to heal themselves, it might become necessary/worthwhile. The critical problem with lightwell nowadays is that enrage timers (soft or hard) are the primary difficulty of almost all fights. With mana mattering, they can move away from that (and GC said they intend to).
First it is in no way a "(potentially) huge buff" that the efficiency it provides would be necessary. It is merely an alignment of mechanics that it becomes worth the effort "possibly". Though if mana situations become so tight that it is really that necessary/effective it could be argued that at that point it is more desirable to bring a healer that has tools that don't have such a restriction. Because frankily most dps players suck at doing survivability tasks.
The issue is that no other healer has a similar mechanic that requires the player to do something to start the heal. There is a history of positioning requirements, group requirements..etc. which are normally difficult enough to coordinate. I expect something will happen regarding Lightwell.
While I agree that the current difficulty to encounters are the enrage timers I don't think that will change. What will change is that it won't be solely a question of do we have the dps... Which invariably in Wrath has lead to lets find a way to swap out a healer(s) to pickup dps. Now it is possible that there will be a limitation to the ability to drop healers because healer mana with less healers my not last to the enrage timer even if it was possible to meet the healing requirement for throughput.