Out of the 8 raid bosses I've killed 10 boxing the only thing I've used more than one tank on is the drake in OS where you have to use the portal.

I agree on how WoW raids are all don't stand in xxxx. It's fine boxing them until you add another mechanic to the fight that keeps you from stacking. It's pretty impossible keeping 10 people out of the constantly moving fire and still tanking/killing bosses and adds.