Using the ally as a mini tank is an interesting idea.
I know about that in single player, killing them as fast as you can. What's your dps? Because unless you're rocking about 40k you're not going to kill that many of them while serenity is up, especially if they're molten or something. I know your'e vulnerable between cool down periods, but those DOTs hurt like hell now, so you're REALLY vulnerable, and arcane is still absolute bullshit damage.
I do find plenty of games with a barb, though there are a lot without. Even with a barb though you can't just stand in molten, usually. I could before whatever happened with the patch, but now I definitely can't.
I suppose you are using deadly reach, though, which counteracts a lot of the DOTs. Thunderclap is awesome for some things (like dps and getting back LOH, etc), but bad for others (teleports you right on top of the damned enemy, so you get hit by whatever DOT is around no matter what).