Vulcunous gives massive dps with battlemage and new support spell blade. (numbers are not out on this, in PoB I gave a Dps modifier of the next best support gem in case spellblade is bad)

Mechanics: summon reaper gets new minion aura gem, and makes enemies bleed for vulcanous dps. reaper gets life regen from vitality, consecrated ground, and tree and meatsheild support will reduce with phys dot by 30% to help keep it alive.

Only required items are 2x Vulconus daggers which were 1c on day 1 last league. with just these and rare items you can have around 3 mil dps

PoB link with leveling trees and a few notes: https://pobb.in/Un-fCsbYsvhR