For AST changes, just potency buff malefic and combust...

[LariaKirin]

Could it not be lower than WHM, but more than current? A 250 or 260 Malefic would solve the problem.

The 500 dps difference most people bring up comes from Titan Savage. A 20 potency increase to Malefic will give you a vaguely approximated pdps increase of 300 (at 50%) up to 400 (at 95%). Which technically does fix the problem of AST being too far behind WHM, but it creates another problem.

The issue with looking at this in a vacuum is that it doesn't account for the other benefits of running AST. Because AST has so much freedom and flexibility with OGCDs, it functions as an enabler, allowing their co-healer to put out more DPS than they otherwise would (e.g.: if they had a WHM partner).

If you look at combined healer DPS parses in Titan at various percentiles, you'll see that AST+SCH is not that far below WHM+SCH. This Malefic buff will, in most cases, put AST+SCH over WHM+SCH.

This would be nowhere near as big of a disparity as it was in SB, but if you're not careful with AST buffs, you might end up excluding WHM again.

[YusiKha]

This would be nowhere near as big of a disparity as it was in SB, but if you're not careful with AST buffs, you might end up excluding WHM again.

And so AST, the most difficult healer to play optimally, becomes marginally more effective at the highest end than Glare-spamming WHM.
It’s not as big an issue as you say.