Use Target_custom_near instead of next. This will prevent you switching between targets if you happen to be on a team with multiple TAs.
Also, you only need it to say Oil or Oil Slick, the target isn't called Arrow, so that won't work.
As for your build, the biggest thing I see is not having Poison Gas Arrow. It's really a fantastic power and one that shouldn't be skipped. I personally like Flash and Glue arrow, but those are a bit more personal preference over PGA.
Finally, here's my Ill/TA for comparison.
Obviously if you want fly, you could swap out Teleport Target and Teleport for Fly/hover.
Munchausen - Controller (Illusion Control).mxd