I would use Heavy thurst> Ring of Thorns> then Doomspike untill 500 tp and Invigorate and keep it going while mixing in our OGCD if I knew things would die at around 30 seconds anything more then that I would combo ring of thorns for tp issue
Just do this ^

GK and BoTD is not really optimal for AoE. If there's like a bunch of 6+ mobs and you're 4thing them and throwing out a 200 potency GK every...25 seconds or so (every other combo), it won't be as much DPS as doing 160 potency every 2.4 seconds. If the hoard of mobs is all below 10% you can pop botd quick and do a fast TTT and Geir, then 10 sec later blow another Geir to finish them off, but i wouldnt maintain the rotation to keep up botd if fighting more than 3 mobs. Maybe if I just AoE'd down a set of mobs and i'm on a new set of mobs and i'm sitting at 300TP and no invigorate, then I may as well, do BoTD+GK rotation because 300 TP would be done in like 2 DS's.