I think the changes that geko has posted should work just fine. I mean as long as the foes eventually tremble instead of just runing for the hills, I think it will be fine.
I understand the concern for it not working well with other powers, but I have been in plenty of different groups to know that there isnt always UBER AoE available anyway and as long as the mobs aren't attacking, it's a good thing
I used ST pre I3 and thought is was an ok situational power. Using it post I3, I like it even better. In my opinion the changes that gecko is claiming are going to make it just fine and a nice addition to the crowd controll of the illusion set.