Couple of bugs with 'powexeclocation target' that may be related.
Firstly, I've noticed that using a mob as the target for teleport will fail fairly often. I think this is related to line of sight issues, but is often seemingly caused by small ground clutter like bushes etc.
Secondly I have had problems using ground patches w/ a mob as the target. In the case of things like tar patch, the power fired, but the patch never appeared and I was left wondering what was going on.
FInally, I have experienced the same behavior with the darkness control AOE hold bubble, and have been able to see the top of the bubble peeking out from under the hill a mob was standing on. Is there, perhaps, a missing z coordinate?
I've noticed the ground patch problems mostly in the night ward missions and wonder if perhaps a new technique was used to develop some of these maps. However, I've also seen it in the multi-story outdoor factory where you must kill hundreds of clockwork. Sorry, I didn't make a note of any of these map names. That may have actually been helpful.