That may be fine, but it feels grafted on. There are powers such as the fear ability on the Inquisitor that should be attacks vs. Will (just like dragon fear), but instead happen automatically.
Is there an example in the MM of an aura requiring an attack roll? As far as I know, auras never require attack rolls, and flipping through the MM I can't find a creature with an aura which has one - all the auras apply a flat penalty or effect.