Well,
That was my 2nd run; I think I could do better on the boss fights after a few experiences with it. But honestly, I share your concern. This group layout can get you by on most stuff. But the down fall is the following.

Void walker tank – Not crit immune, no much armor requires a lot of attention on healing. Not much agro tools.

Healing – Spamming void walkers with heal is required and not a good thing. Because they take so much damage it takes a lot of healing which turns in to a lot of hate.

Dps pulling hate off voidwalkers – Catch 22, if you DPS slow you healer gets agro from all the healing to the void walkers. DPS fast then your DPS gets agro.

DPS and CC Pretty darn great, I think. It just lacks strongly in the tank area

No matter I'll make it work!