Please tell me that was a sarcastic question. Does this LOOK like a non-raid mob? Does this look like a 3 group mob? Of COURSE it's a raid mob. Again....I hope that was a sarcastic question....or you are new to the game and/or aren't in a raiding guild....because otherwise, I would be afraid....very very afraid....for you, if one or all of those suggestion's are not true. Sorry...I'm not a flamer usually, but that question just baffled me.
Pretty sure they classified it as common because if you can manage to kill this Bertoxxulous (Plane of Time), the belt is a common drop as opposed to some items on the loot table that will only drop occasionally or rarely.