Summoned at all times:
4 or more zombie dogs
Templar (or other follower)
Potentially 1 or more Fetishes hanging around most of the time
Rotate your 2 big cooldown spells for huge groups of mobs and during boss/champion/rare fights to summon more trouble (Confusion and Fetish Army).
Mana will be spent spamming Firebomb with Flash Fire (extra bounces), with Pierce the Veil providing a big damage boost for this skill since it bounces many times. Firebomb also has a chance to summon another Fetish due to the Fetish passive. You should have plenty of mana since there is only one skill which you will be using all the time (Firebomb) while managing your army.
There is probably a better way to have a maximum amount of pets, and some runes or passives may be swapped out, but this looks fun and hopefully will be somewhat viable. If the zombie dogs just don't survive much past normal, then I would probably replace them with the Healing Hex guy which supposedly heals allies (Spider, Follower, Gargantuan) as well as yourself. You would still get zombie dogs every now and then from the Confusion rune but nothing to really rely on.
It would be sweet to approach a boss with 7-8 zombie dogs, a spider queen, follower, gargantuan, a few fetish, and then pop fetish army to summon more when the fight begins. Hopefully one AoE won't kill them all too quick.