I put points in Corpse Explosion, and in Hortimonculus last night.

Corpse Explosion seems to takeforever. The corpse just ignites like a campfire and then blows up a few seconds later (not very graphically, alas  ), doing extreme damage. Might be useful in base defense/assault when the battlefield's really crowded.

Hortimonculus turns a corpse into a healing/power restoring plant of sorts. You can also click it (like it were a quest clickie) to  heal. I don't think it'll be very useful, aside from maybe dropping it inside a base during defense (otherwise it too easily can get wiped out on the battlefield).