No...I just laid out how WHM can have superior oGCD healing to SCH as well as superior offensive GCD's over SCH. You can already see an example of this in Neo Exdeath, where the fairy's embrace becomes fairly useless in terms of covering the needed healing - WHM edges out SCH for damage and is vastly superior in healing for Neo.

All they really need to do is buff SCH's adlo/Succor a bit and WHM's offensive damage by a little, and leave Astro the same. This gives SCH the option to handle the brunt of GCD healing by themselves, while also giving WHM's a stronger offensive role while still being able to being top-tier GCD healing when needed.

They've already given a role to WHM - they choose to either do the best DPS of all healers or the best HPS of all healers, but they can't do both effectively. The issue is that their hardcasted heals are so good right now that it's more efficient to just make the AST/SCH go pure DPS and have the WHM handle all of the healing.