Seph with haunting on average you are going to be able to kill 1 mob every 15 seconds regardless of your dc.
If you kill something and then kill something else before the 15 seconds you now have 30 seconds of debuffs to wait out. If you push ahead of the 15 sec per kill the system brings you back. This is regardless of dc/gear anything. So why gear out. Why strive to be better. Why spend destiny points on lower necro cooldowns or better dc's? Why go tier 5 illusion archmage for a second pk. Why ever even carry circle of death as an arcane, or slay living as a divine. Why not just be an evocation archmage or better yet a sorc.
There is no class in this game that should be limited to one kill every 15 seconds.
I am not one of the so called people that never want a nerf, I was one for saying helaing amp needs to be looked at with some of the values out there and the difference between human/half elf and other races.
However I do know that instakills are not the issue here. Sorcs are just as adept at killing things off fastly and for some reason melees think they are cooperating with the sorc when they both do dmg but regardless the sorc doesn't need the melee there for any reason.
Same went for before the change to epic ward in epics and these spells werent allowed I was soloing into the deeps and many other epics before than (often inviting in people for the end fight/chest) I once killed 750 tieflings in echrono (got 3 scrolls grr) without deathspells and didnt need a single melee to do it.
Haunting is a flawed mechanic because it attacks the wrong end of the problem. While instakills can be problematic and could use a small tweak it doesn't change the fact that melees are extremely inferior to casters. It just changes the flavor of the op caster.