I wouldn't turn this into a WHM vs. SCH grudge-fest, tbh. The OP has some valid concerns, and Sleigh highlighted some REALLY good points about how what SCH is bringing to the raid table currently will benefit progression-oriented groups way more than the brute-force healing of WHM will. If Astrologian's Disable acts as its own Supervirus then it will at least be POSSIBLE for WHM/AST comps to survive raid busters like Gigaflare/Nerve Cloud, but I still suspect hardcore groups will roll SCH/AST if those effects stack.

Essentially, SE wanted to give WHMs and SCHs more "mirror" skills of their counterparts - ie, SCH got more raw/burst/AOE healing, but the difference is, SE gave WHM more "instant cast" heals and some DPS increases rather than supply WHM with what they were truly lacking in an endgame environment - raid-wide mitigation. An easy fix would just be to allow Stoneskin II to be cast in combat...it has a long cast time and a huge MP cost, so you'd obviously only use it for raid busters, not just spam it all the time. I really don't understand why this wasn't considered from the start.