Well, once mitigation got evened out, and there is not a single fight balanced around needing paladin's mitigation (or really, any of their other tools), aside from LB issues and possibly debuff application, there is no reason not to bring the highest dps tank.

Which is why...the reasoning behind why pali is behind on dps makes me sad. PLD's loss of dps is way, way higher than the amount of dps a healer would gain from healing a marginally easier to heal tank.