Just finished the quests. Apart from all the things that other ppl said in this threat i suggest abusing the imps for ember generation and keeping them alive as long as possible. FnB immolate + RoF on them provide sick ammount of embers which allows chaos bolt spam, u can easily tank the imps with sac pact and loads of shields from soul leech chaos bolts.
On 2nd imps i downed the boss from 21 to 0% just on SB spam with DS up.
Felhunters were trivial once I LoS'ed the pitlord and burned puppies with DS, shadowfury and all def cds up.
Although i must add that this was done with 506ilvl. I imagine that with lesser gear that would require more coordination.