The short answer is that power lies in crit range and to a lesser extent crit multipliers. Pally gets these, but only on activated abilities. Other classes get them all the time. Pally can't compare. Rogue, Monk, fighter, even barb and bard all have permanent or semipermanent crit range or multiplier boosts built into their trees and pallys do not.
As a suggestion, pallys could get +1 crit range with bastard swords (and shields too, why not) at tier 5 defender and +1 crit range and multipler with longswords at tier 5 Knight of the Chalice and we might have some meat to start building around.
My opinion is that every melee class needs a crit range or multiplier boost built in somewhere, even if it's just on niche weapons, to stay competitive.