1 Necro (Blood pref.)
2 Warriors
The things you need are, people with brains and time.
We have totally finished off SF (except for the Furnace Guardians) ... we died a few times but what the heck we made it

I was the Necro and I took the following skills:
Vampiric Gaze
Life Siphon
Rebirth
Well of Blood
Vampiric Touch
Shadow Strike
Rotting Flesh
Life Transfer
My Attributes:
Blood Magic 16
Death Magic 9
Soul Reaping 11
Well at first we were with 6 but in front of SF 2 left and we decided to continue to see if it would work with 4 people and it did.
Well it's best that you have experienced people and people that know stuff about luring with gears and stuff like that, every other knowledge is a +.
Hope you guys can use this somehow, good luck ;p
Ingame-screenshot of us 4: