I think you're making it too weak.
Should be:
But honestly, I think I agree with the person who said it should basically not change too much from current, just be less clunky.
A single click power that activates a -Res to All debuff on the enemy, that can be activated DURING other powers animations, and grants the Sentinel both the Defensive and Offensive portions of the current buff, but with the Offensive portion enhanceable and buffable.