It's a bit sad to see vortex go from "fly like a bird, little Grineer!" to "lie down there for a bit".
I've noticed a similar problem with the vortex phase, when the attraction point is above ground level: The mobs just lie on the ground and twitch. In terms of pure effectiveness for crowd-control, it's equal, but it's much less fun. I mean, if you're going to gun down a Grineer for points, at least let them fly like a bird first...