Seems to be missing that "Level 1 cleansing aura while equipped" or "Level 8 resist fire aura while equipped"
Everyone wants to use an aura weapon and aura helm, which leaves no % life leech on any slot except armor, which leaves the only possible options as CoH, greyform, skin of the flayed one, boneflesh, and a crafted blood armor
I'm making the argument greyform with a protector's stone in it is arguably the best in slot option. A bit less damage/leech than COH in exchange for fade, which matters in the very long TZ herald hunting games.
Those auras are not worth having a wimp merc