Pets can now taunt aggro reliably since the Feb, 2016 patch where they fixed pet taunting. My wizzie mercs regularly get aggro but the pets can now taunt it back. The more pets you can throw with taunt capability the more likely your wizzie mercs will survive. I'm pet tanking named mobs in all the TBM zones without an issue. In order to keep things stable early in the fight I start each fight with the wizzies on Balanced and only switch them to Burn once the mob is debuffed and slowed. The "fat pet" is our family name for the Remorseless Servant limited duration high damage (at high mana cost) pet. I think my wife coined the term way back when the early graphic for it was quite large. Doing progression and hunter through TBM I've been boxing mage, chanter, cleric with all 3 having wizzie mercs for most content and switching 1 wizzie to a healer for namers and groups of non-mezzable mobs. A fully equipped chanter animation pet with hate swords grabs aggro quite well with the mage pet grabbing it back usually a tic later. The chanter and cleric are raid equipped but the mage is only group geared although the pet is up to Minion 19 from a Rain of Fear raid drop. 2 of the 3 wizzie mercs have all their subtlety max'd and it makes a big difference!