Ast also has a lot of Stigma to get past as well

-Healer stigma in general of being dull 1 nuke 1 DoT for downtime when heals aren't needed.
-New card system is underwhelming
-The reward is not worth the effort over the competition
-Controller issues especially when optimising
-Gameplay doesn't reflect lore

The devs have only addressed one of these, that being the reward/effort with Ast now being the strongest healer but the biggest one keeping Ast numbers so low is the controller issues, this problem needs to be addressed asap yet they will not even acknowledge it and thus the stigma will remain for most of the expansion alienating people before touching it.