These resurrected corpses can only be harvested for some top-quality materials or used as material for the Corpse Explosion Technique.
As for using the Necromancer's ultimate ability "Rebirth" to resurrect the corpses again, forget about it.
The "Rebirth" skill requires a strand of residual soul and a relatively intact body, but these corpses, resurrected by some Rule, don't have even a shred of soul left; they've been drained completely clean.
Moreover, after being killed again, these resurrected bodies will not drop anything; their only value is to become the shell for an Epic Boss.
Dragging them back to dissect and distribute the parts, one can obtain quite a few epic materials, which are highly prized by many Life Professionals.
At least Dilys and the four sisters of the Fan Family would definitely want them. Array Masters and Alchemists have a much higher pursuit of top-quality materials than he, a Necromancer, does.