Originally Posted by
Mugajak
Because you have limited need of tanks and healers. I can't think of any encounters that can use more than say, 3 tanks (you could argue 4 for Mel'jarak if they wore DPS gear and went nuts with the vengeances?), or 3/7 healers by encounter for 10/25, and once you have those, you've got a few spots left for pure DPS. Or many spots, for 25s. Why bring a rogue? Well, if you need the buffs/debuffs, you need better cleave, better sustained single-target... leather wearers to spread through the raid?
I fully agree rogues NEED more in the way of CDs, but there's no reason NOT to bring a rogue because it isn't a hybrid. My warlock is feeling plenty loved as I top charts on every fight, bring health stones, the occasional portal, and do upwards of 5k HPS on myself (10). The reason you wouldn't bring a rogue isn't that they can't become a tank or DPS (oh hey symbiosis!), but that other DPS bring better CDs. The night we had a Spriest with symbiosis and a feral with HotW saved for healing, the entire healing side of any encounter became a joke; 3 extra healing CDs just provided way too much flexibility we didn't have before. My rogue can't bring that.
Note: I think it's both an issue that rogues DON'T have any raid CDs, and that other classes have that POWERFUL of a raid CD.