Is this viable?

I've started a necromancer for end game and running through the levelling up right now, only 10 levels to go now!

I've found even just as a quick build , having reapers with as many as I can , blizzard mages and 3 golems with the bone ultimate on them to be pretty effective if not fully damaging (helltides do outpower me eventually).

My question is, how can I build into that for end game to be able to massively up the damage of the ultimate and have an army that will mob control at the same time?