The hardest thing about slotting new classes into the controller role is that we only have one example so far. Every other role we have enough classes to see different ways the role can be filled, eg--
Defender Fighter wades into melee and kicks the crap out of anything unlucky enough to get within reach, while the Paladin is throwing around radiant damage and handing out buffs/penalties to make attacking anyone else tactically unsound.
Striker Rogue skulks around the battlefield, slinking up behind people and knifing them in the kidneys, while the Ranger shoots them full of arrows from long range and the Warlock uses his arsenal of magic blasts to target different defenses and attach crippling rider effects.
Leader Cleric seems more focused on healing and buffing, while the Warlord is playing chess with the battlemap.
Controller Wizard does...wizard stuff. Obviously lots of focus on AoE damage and stuff, but since we only have one controller, and the Wizard is getting totally revamped so that we aren't even sure what all he's capable off...hardest position to fill, except with classes that are already wizard knockoffs.
I do agree that defender seems best fit for the Barbarian. Make him a lightly armoured, blender of death defender, sure, but he's still a frontline guy.
A leaderish-defender, incidently, would probably be stepping on the Paladin's toes, even though the flavor is completely different.