player use: generally this runeword won't be made for vast majority of players in trade leagues, I would say. you could just trade for a better unique or oath. if playing a self found only melee play through, however, this is a great option to plan for. until you could get oath or better.
merc use: hard to say. taunt is a single target cast and doesn't work on bosses. this imo makes it pretty bad. i wish it was chance to proc battle cry, an AOE spell. would've made this actually strong. although, maybe blizz has other changes to the A5 merc in store for us. anyway, still going to be dam tough to beat A2 merc with his auras - they're just too good. if taunt is trying to be defensive, i'd rather just have holy freeze to slow the monsters.