"Onyxia is deep breathing more" is sort of the end-all be-all of generic post-patch raiding complaints, kind of like how "Kite him to Vael's room" is always offered as a strategy for any new boss. These comments are generally met with derision, since a. Blizzard really doesn't have much of a reason to change Onyxia at this point and b. if you spread out and do enough damage to Ony, you won't get deep breathed, or so conventional wisdom says.
However, Maeda of Homegirls offers photographic proof that something was a bit ... different with Onyxia this time around for her guild. Nhaerl, of the Feathermoon server, chimes in with his screenshot. Luckily for all who still fear the big black wyrm, Yaltus provides a reasonable explanation -- possibly the first ever seen on the WoW forums.
Have you noticed any older bosses acting tetchy since the patch?