Honestly?
- Either up the CD timers of abilities or increase raidwide/unavoidable damage so I am not using the same CD for everything.
Ex: I stated earlier I can use Exaltation 100% over Celestial Intersection for tank busters in just dungeon content alone because they come ~ every 60. If Exaltation was every 90s I'd instead use CI. Conversely if another tank specific attack happened in the same fight in under 60s that would make better use of Exalt (perhaps a short heavy bleed) I'd use Exalt there and cover the next TB with CI because the shielding was better.
- Prune redundant abilities by making them into upgrades at higher levels while still keeping them at lower levels.
Ex: There is no better example than Benefic and Cure 1 to Benefic and Cure 2. The trait for it would be hard to place, because I believe WHM has some issues with Cure 2 straight up overriding Cure 1 in some situations... but that is something that better skill leveling touches imo.
- Allow parts of our kit to play more with one another than just X
Ex: Good one for AST is Synastry. I love the ability. It only works for Benefic why? Instead of two CI charges Synastry can be used for it to place CI on both Tank/other target along with ED, A.Benefic and pretty much anything but the cards if its single target (unless you want it to also work with cards and/or Astrodyne and deal with the rebalancing headache that can cause)
- For a more opinionated take: Make healers actually diverse.
Ex: Shield and Pure healers have abilities that overlap for imo no good reason. AST can be a regen healer just fine. Make it one please.