I run a one pet (matriarch) storm sorc and am perfectly happy with Necropotencex5, Julianosx5, Slimecrawx2. Extremely easy gear to obtain and plenty effective.
For what it's worth, I run 5/1/1 with infused on big and divines on small pieces. Apprentice (+ spell damage) Mundus and dual shock staves.
Necro + Mother's Sorrow. Its really the best combo. Both are overland sets. You can get a MS lighting staff from "The Ravaged Village" quest in Deshaan (or you can get ripped off by a guild trader). Then go ahead and farm dolmens for the jewelry. Or run them in reverse if you can get a pair of Necro lightning staves.
As for monster sets, Zaan is best, but Valkyn Skoria is a nice close second. Iceheart is a great set for solo play and procs a lot.
You can play around with other sets. Someone mentioned Infallible Aether. Fun set for heavy attack builds and relatively easy to farm out of HRC. There is a build that uses that with Undaunted Infiltrator (xynode), but I've found getting the jewelry and lighting staves out of Arx is a pain. I ran IA + Elegance (Auridon overland set) and had similar results as with Undaunted Infiltrator, and since Elegance is a light set, you can mix and match (UI is a medium set).
There are plenty of other sets out there, but they are a bit harder to obtain than these. One of them is False God's.
EDIT: But when all is said and done, for pet-heavy builds, I don't think you can top Necro + MS. Its REALLY good.