@Pyromelter

The reason the aoe became so good was that tanks finally picked up more aoe threat abilities and threat changed in a way that tanks almost never lost adds, therefore why cc if the healer can just heal through it. Prot pallies started it and soon enough every tank got the ability to do reasonable aoe threat, the problem is when mobs do so much damage that they cannot be aoe picked up then cc will be needed again.

As for healers never running oom atm its because of how gear scaled in wrath + extra tiers of gear that were not planned for (hc gear) so int + regen stats became too high. For cata they seem to want tanks to have a much larger hp pool that will take many hits to empty but which will also take many more heals to fill up, unlike the whack a mole style of healing we see today, if tanks dont die in 1 shot and require many more heals to fill their hp bar, and less regen stats in theory we will run out of mana much quicker than today so in some ways i reckon blizz can pull this one off and not just be a complete failure.
For example lvling in dungeons atm for healers is quite well tuned for the wrath dungeons, very rarely can i just sit there spamming heals and not run oom, because the regen on gear and the damage the tanks are constantly taking 5mans in cata will likely be the same when were using raiding gear ofc were not going to run oom, but for the first month or so it should be rough on the healers and for end game content it should be just as hard for us healers.