actually mutiliators do the fewest hits
blighted ones have the highest cadency with roughly 80% more hits per time than mutiliators with life stealers not far behind (roughly 70% faster than mutis.)
this comes into account when you wanna procc things with your pets; like 'Resonance' (tos' idol of sets supremacy), Bone Horde (necro skill) a Templars Aura of Dread Fury (which can actually only be procced by Life Stealers and Blighted Ones and not via Mutiliators!)
-> Thusly Mutiliators arent Jack of all Trades - as they're often presumed to be;
well, as this is not of prior interest to the opener i may just add some lines to increase your questing experience:
first is: never go out without at Least 2 Melee pets while questing -> reason is your 'Aggro' Pet (cast: Frenzy); this is one of the most comfortable things you can get for questing since it makes enemies engaging your Pet instead of you; plus it adds a nice unholy debuff on your foes which increases your flesh to worm, mark of the devourer or blasphemic ruin Damage for example.
this skill can be enhanced further in the reanimation tree (third line "unholy fortitude") making the skill available quite often.
apart from these 2 melee pets choose whatever you want; keep in mind that the effectiveness of some abilities decreases with the amount of pets of the same kind: you wont heal double the amount with 8 life stealers instead of 4; mutiliation doesnt increase linearly though you need at least 6 mutiliators to stack that procc (a procc not a dot!) to 10 consitently, etc pp.
so if you run with mutiliators run with at least 6 or dont use them at all; if you run with lifestealers dont take more than 4; add a few blighted One's to get the soul torment debuff on your foes quite fastly or add 3 Casterpets + 2 Melees if you feel like it