With the current LON Witch Doctor, I don´t see any change in the "meta" except for the Boss Killer part. Groups are reaching Greater Rift Level, that were only possible with the most overpowered class up till now, the Twister Wizard. With everything I´ve seen on the PTR, the Necromancer doesn't offer that kind of damage output on multiple targets. Especially considering, that the Witch Doctor is doing all it´s damage without the need of Area Damage. Therefore server friendly.
On the other hand, I think the Necromancer has the potential to be the new Boss Killer. With the Wizard being stripped next patch due to the whole stacking fiasco at Rift Guardians, the next obvious class would be the Demon Hunter, which would lower Greater Rift Levels to maybe 126 again. I think that won´t happen.
The Necromancer has some unique skills/abilitys, that I guess will be vital for group composition (Boss Killer) next patch:
- Frailty (with less than 15% Health, the Enemy just dies) - Holy Shit!
- Convention of Elements with just 3! Elements on it. - Oh Jesus
- Life from Death - Health Globe Spawn - Synergy with Witch Doctor
- Most of all : Unknown Stuff that hasn't been tested on the PTR