This is also my #1 pet peeve. If your team has no damage mitigation aside from "taunt mobs to stay on the tank and scrapper", okay, sure. But if your team runneth over with control making the enemies helpless (and preventing the tank, and everyone, from getting aggro), debuffs making the enemies simply anemic, or buffs making your team members unstoppable gods...
And, granted, your AoEs WILL be more valuable if you stand and wait for everyone to get grouped up - sure! But, are they so much improved that it's worth having 7 team members sit around twiddling their thumbs while one player plays the herding minigame?
Also don't get me wrong - I love tanks and I think tanks definitely have a role on support and control heavy teams - it's running AHEAD of the team, pulling more and more mobs into the death zone. Because why steamroll one spawn when you could do three?
Both Brutes and Tankers can excel at this task, it just takes a little more slotting to get the Brute there.