Killing a vox with thermies

After repeated dying to this thing, ive found 2-3 thermites to that under vent pops them. Been running supprt pack to keep up thermies but as soon as i see one drop im immediately gunning for it before it drops and starts that whole hellfire missle or instalock death laser b.s. but yea if you can get under it right as it drops and hit that vent with thermies, its no issue. The issue with that though is if your being targeted by another vox, those n missles can and will still hit you under the one youre after because somehow the missles phase through it. Also gotta be sure that thing isnt swarming with grunts (the warrant handles that part)