Cudge

On one MM I have AM slotted with 3 recharge, 1 acc, 1 Achilles heel, 1 def debuf

The other traps MM I have 3 recharge, 1 acc, 1 Achilles heel, 1 damage proc (forget which type, it was a recipe that dropped after a mission).

I've seen the AM with the damage proc deal a killing blow every once in a while - gratifying. For me the answer to the question is 3 recharge, 1 acc, 1 Achilles Heel, 1 your choice.

I have a lot of MMs. Only three made it to 50, two Merc/Traps and one Merc/Pain. I love my mercs.

On one Merc MM I have invise other. Nothing like an invisible army and they don't agro things when running through mobs.

A lot of groups don't want MMs period because most MM players don't exercise good pet control with agro. On the other hand my Mercs don't need a group to kill things - they are a group.

The only disadvantage I see to Mercs is that Lethal Damage doesn't do as much to higher end mobs. But as others have said, slotting Achilles Heal in the pets (and in my acid mortars) helps.

Besides, I like all the gunfire and spent rounds on the floor.