Game Mechanics: Necromancer pet aggro

[Scrubosaur]

There is something not right about the way pet aggro is working on p99 at least for the necromancer pets. At low levels I figured that it was just a low level thing but now at level 37 my pet (level 34 invoke shadow) is unable to hold aggro on greens mobs after it tanks them to 70%. It is pretty easily repeatable, I was in Nek forest hunting shadow wolves for the pelts and was also killing Willowisps (level 9-11 according to wiki). I repeatedly sent my pet in to attack (gaining initial aggro) and my pet usually did first round damage that knocked the Willowisp down to 60% to 70% health. I cast level 29 spell vampiric curse and before it even ticked once the mob ignored my pet and ran to me. I seem to remember being able to out aggro my pet using the debuff dots (heart flutter) or snares but never on a low damage low resist spell like the vampiric line.