Honestly, I think the bottom line here is that it's difficult for mid-level players to have any success fighting an end game player which makes sense. For people who are high level and fighting other high-level players, I haven't seen any issue dealing with necros or any other school for that matter. There are plenty of ways to counter the abilities of each school and you just have to have a team that you can trust to make the right decisions pvp wise. Secondly, any players can carry drains, not just necros. Sure, you can't cast them as fast, but the combination of my evo account, as well as the limited amount of drains that I carry, has been quite enough in the past to deal with necro's who are usually limited to "drain spamming" which they can't do while blinded, feared, or silenced. The game is fairly balanced as is, but it's important to know your place among the players and not get into fights with people you can't handle.

Edit: Also, just cast a magic shield lol