The damage comes from the Blightfiends (you get +1 summon with that set), Hellhound, and Talon. Stacking Vitality RR, converting the Hellhound damage to vitality with secondary damage being Poison.
I’d have to play it and see the survival/damage to know where to finesse the points. You are probably right and if you minimize all the points in familiar except storm spirit you can dump them into raise skeletons, reap spirit and call of the grave. This will give you a lot more damage, though the skeletons will still die fast, though with 4 tanky pets (2 blights, revenant, talon) to keep the pressure off they should have a chance.
The Ghol set is new in FR. I’ve had 2 pieces drop, so I imagine its just like any other mythical legendary set, except with the bonus of using the inventor to transmute to complete the set faster than usual. Especially if you happen to get a helmet blueprint you can just make your whole set from hats if you have the mats.