I really like the improvements they made to necromancy, so that's my primary of choice. The tougher decision would be which secondary to go with. I very much like kinetics, but I also find its reliance on enemies to be burdensome. In the same vain, while elec affinity is great, its chaining mechanic also adds a layer of complexity that may not be to everyone's liking. Pain domination has some great healing and buffs, benefits you as well, and world of pain can just about be made permanent. I don't have any significant experience with thermal radiation, but it appears to have a great balance of resists, (which necromancy pets already have), and heals, but lacks world of pain's ability to buff yourself...