To be honest I'm rather surprised that AST is the target of buffs. Maybe it's not fully realized with AST being the least popular healer, but it's currently the strongest by a mile. It has amazing tax-free heal power, mobility, weave windows, raid buffs ...everything the other two lack. If they give it mana regen and lower APM on top of that, it'll be almost flawless from a performance perspective.
If you look at the top clears for Savage, they're almost all AST + Other. This isn't min-maxing, it's simply because AST works far better with WhM or ScH. AST has the heal power to take the bulk of raid healing with free oGcd's, which mitigates WhM/ScH's need to pay heal taxes and clunkiness. A WhM/ScH can take a bulk of healing too, but unlike AST the more they take the more damage it costs. With a WhM+ScH comp, someone has to pay the cost to keep the raid alive. In particular AST works well with WhM because it allows them to use lilies as a movement/weave tool, demonstrating how badly WhM needs this.

It seems AST isn't unpopular due to power, but more to gameplay and the changes, so that should really be their main focus.

Also WhM seems to be the most popular healer by a good bit and there's something in that. I'm not sure just because it's easy (more despite that), but because it functions more straightforward. ScH especially is like a WhM with half your oGcd's tied to a clunky, glitchy mechanic that switches itself off for 30 second windows. The pet in its current form is more hindrance than identity and hurts what should be an amazing toolkit.

I'd like to see them address ScH's pet and WhM's weaving first, but for some reason it's buffing and reworking the top healer in the wrong way. It's a bad sign if they're still this out of touch after all these months of feedback.