Not that I've noticed. I walked out of the Nexus the other day and quests for half an hour with GotW (I'm a hunter).

quested*

damnit, ADD EDIT BUTTON

If you mean when did group buffs disappear when you're no longer grouped, I think it depends on the buff. Fortitude, the spirit buff, and certain other buffs remain intact... At some point during BC, since I play one, I know they changed the Paladin greater blessing buffs so as soon as you disband, the buff goes away. Not sure what other buffs were affected. Seems to be the buffs that you can only cast on someone when grouped with them.

Regular buffs will last but if you get the improved buff in a group you will lose blessings, Fortitude, and Gift of the wild, Divine spirit stays but I'm not sure if thats intended or a bug.

The group buffs have been fading for a while, but I've noticed it happening a little differently. When you ungroup, if the buff has a duration that is shorter than the single buffs, it will stay with you. I.e. if you have arcane brilliance, but the buff duration has dropped to below 30 mins, then you keep the buff when you ungroup because a single buff can last its duration. This also happens with pally buffs, but people are less aware of it because of the reduced duration to begin with. If you have a greater blessing on, but it has less than 10 mins when you upgroup, then you'll be able to keep it.