It's particularly the nerf to AoE healing that causes problems. Wild Growth literally ticks for like 1% of people's hp while the fights seem designed to domoremulti-target damage than ever before. The fights are often a complete clusterfuck and the healer has to put in a 110% work effort in order to stave off a wipe. They needed to make mana matter and they needed to do something about smart heals because they were too easy to use in raids, but they also chose to just make healing a lot weaker in general for some reason.
Having 630 or better in every slot, mostly with optimal stats, half of the heroics still feel like I'm severely undergeared because healing is simply that weak. We don't usually wipe in heroics, but there's a lot of deaths that simply can't be helped because healing that much isn't mechanically feasible. Anything that isn't your big single-target heal (which is either really expensive or really slow, depending on which one you choose) heals for so little that it can only be used to patch up minor stray damage. In many of these fights, I simply cannot stop chaining heals on the tank for a moment unless he pops a cooldown, which you can only do so often.
I've tried a couple more challenge modes since the last post, and although I know I play the class adequately and my gear is literally as good as currently possible short of buying insanely expensive BoE epics, the boss fights often feel mathematically impossible to heal. The damage simply exceeds maximum possible healing output for the class combinations I've tried thus far. I'm not failing to make use of some source of healing, and it doesn't seem likely that all the tanks are playing wrong, healing just feels about 25% too weak while the fights are simultaneously designed with much more AoE and movement than before.
