I have to disagree. As a Bodyguard specced Merc I outfitted Blizz in all DPS gear, and keeping him in tank stance I've been able to solo content 4 or 5 levels over my head. The trick is to keep constant uptime on your heals and buffs and micromanage his targeting so he can hold aggro. It's basically the same way you would use Torian, but with a much easier time holding aggro. He also seems to have more mobility than Torian or Skadge, and I like that a lot. He's probably my favorite BH companion, if a little hard to use at first.