Well, we can't really balance jobs around "ifs" and "buts" though can we?
Unfortunately you can't have every job buff it's own damage type as that would ruin party synergy as well.
SCH can DPS almost indefinitely using Aetherflow and Energy Drain. MP Cost + MP recovery is really close.
WHM can solo heal without Ballad with the occasional DPS added in for all DF encounters.
Not sure where AST stands.
In the case of a healer death or a healer having to Raise + having MP issues reduce BRD/MCH dps by another 2% for ~42 seconds of Ballad to get them to their next MP recovery CD.
Paeon + Ballad 90 seconds total time -> 4% damage reduction over a 6 minute encounter. Even at 4% DPS loss that could be the difference between a run with lucky crits or not.
So for almost all scenarios, BRD/MCH are penalized very little for their utility. The most impactful being having to use that utility during AOE scenarios where they really pull ahead in DPS ability.