A brawler should support the main tank with tanking making it easier for him! Something like a stone to lean on incase the mob has a knockback to prevent him from taking off. Someone that has a 100% chance to intercept an attack with 0 dmg done to either, but would be on a longer recast. .....
Someone who will prevent the tank from going down and wipe the whole raid. Someone who generally helps the other tanks tank better!
We can do this already with normal CAs and through AAsWe save the [expletive haxx0red by Raijinn] slapping for the rogues