Going Necro-only will be tough early game, as you won't have access to many damage skills. If you want to make a beast from your Necro, go Warfare+Necro, it's devastating, but only after you can cast Grasp of The Dead and/or Blood Storm.
Necro/Summoning will work great (go for 10 summoning first, then go Necro). So in your case, you can just pump into summoning and make a blood summon.
I found Scoundrel to be very fun and powerfull, as you should invest into scoundrel and warfare, you have access to a lot of CCS and they will outdamage your other physical character at first (but will fall off in the mid-endgame)
