What I'd like to see is a combined version of the three debuff skills. Still single-target, of course, to fit in with the theme the priests already have. Or, at the very least, adding a 2-3 second 'debuff prevention' for each type after having it cast on the person, just because AoE mobs get really old, really fast with debuffs.
I'd also absolutely love to see a skill that specifically reduces the agro acquired from healing -- possibly even targetable, so Priest/Sage pairs benefit, and even Warlock/Mages can get a little benefit from a Priest. Or, a combined version, that is both a self-buff and a targetable buff in one -- the self buff could add 25%, while the target would allow 75% (thus meaning the Priest would be able to heal without drawing agro, but wouldn't be able to give 100% to Sage/Warlocks). Again, mainly thinking about AoE mobs, and especially for HoTs in those situations.
A passive Damage Reflection targetable buff would be hilarious, too. Be offensive by being defensive, huzzah! Granted, the actual value would have to be tweaked pretty hardcore to make it balanced for PvP, unless buffs can have a pve/pvp distinction in them.
I definitely agree with the suggestion to remove the damage limit from Cognitive Shield. It's not like the skill can be spammed, anyway. Of course, I'd suggest this be applied to all classes that have a similar type of skill, too.