Against a large group (5+), Doomspike is more efficient than HT-ROT. Both DPS and DPT. However, if you're chain pulling many large groups, you will simply run dry from Doomspike spam. As a result you simply need to revert to HT-ROT for a lighter TP drain. Sidenote: you pretty much never want to ROT spam without HT.

Remember to use your OGCDs while AOE spamming, mostly Leg Sweep, but Jumps as well.