Healer DPS potential is greater than tank DPS for AoE (except Scholar. Lol, delete Scholar from the duty roulette) so you should prioritize Clemency over DPS for large pulls provided you have a healer who DPSes.

That's because casters deal higher damage for the same amount of potency to compensate for having no auto-attacks (I don't know if this is why SE did it this way, but that's how I think of it anyway). However, you only want to use Clemency over Holy Spirit if your healer is out of Assize/Tetragamaton or has already used Essential Dignity because these are essentially free healing.