Honestly why not give it the same treatment as Titan Barrier and have it damage enemies that walk into it. I've always thought Warlocks were meant to be the zone control mages, so why doesn't their rift work similarly to Witherhoard? If not then simply unify the animations, making both rifts use the Empowering rift animation (One it's cooler looking & two your warlock ducks when casting it) along with speeding up the cast animation so we aren't locked into it.