People keep bringing this up but I doubt it will be an issue. Could you make 6 necros and try to tag named mobs? Sure, but even with automation doing the tagging it would be tough to pay attention to all 6. Once the mob spawns and you get the tag you still have to kill it, and for the most part, killing stuff with a necro (assuming you don't massively outlevel the mob) is a finicky process. They can do it, but they need to be played and played well. You just aren't going to be able to spread your attention out that much successfully. It won't be worth the hassle. All a group would really have to do is leave the PH up while a necro was sitting there. Now the necro has to spend even more effort killing the PHes, reducing their ability to snipe other mobs even more. And it will still come down to who has the best ping and insta cast items, the group has 6 chances to have a better ping than the single necro. Assuming that necro isn't distracted killing a mob on another character.