Really too early to say. There really wasn't alot of 4 man testing on the PTR since most people spent time playing the necro I tried to get 4 man runs together but it was hard to get people to play support or other dps classes to get a true sense where the necro will fit in.
Likely monk will still be in every 80+ gr since there is nothing better for heals and grouping.
2nd support is unknown -- Barb is outstanding for scouting and damage and damage reduction buffs, BUT there is a necro support build that is insanely tough and can do some significant damage. It is not clear how far this will go yet -- but the barbs spot may not be guaranteed
dps -- nothing new on the existing classes, but still up in there air where the necro fits in. I have a feeling no matter what there will be a spot in a group for the necro for the frailty curse, most likely as trash killer role. I don't want to see the necro forced into a support only situation but it is possible based on DH rg killer ability and the WD LoN insane dps.
There is likely to be some changes over the next few weeks that will make this only guess work right now. I have a feeling the likely changes will be more overall survivability to the necro dps builds and nerfing out the invulnerability build. I wouldn't be surprised if the WD LoN build gets knocked down a bit too.