According to FFLogs, AST pDPS >= WHM pDPS in 4.3

[Exiled_Tonberry]

Minimal party-utility but maximum raw healing output.

Dark knight has max single target mitigation...SAM has huge melee dps output, BLM has huge ranged dps output.

This is how it SHOULD be. The reality is, DRK isn't the best at even single target mitigation, SAM isn't the strongest melee and BLM isn't the strongest ranged.
WHM does indeed have the most healing throughout readily available, but how often do you need more than what a SCH or AST offers? And they can reach such healing numbers without aggro issues.