WoW Insider posted previously about the changes coming in to reinforce the point that 14 is not some magic number for Siege of Orgrimmar Flex raiding. Lead Encounter Designer Ion "Watcher" Hazzikostas has posted on the official forums once again to clarify that the recent hotfixes reinforce that position.
You can read the latest hotfix notes here: http://us.battle.net/wow/en/blog/11944164/542_Hotfixes_December_16-12_16_2013
Fun fact: The hotfix has actually been active since just before the weekend, but it didn't get caught in the prior round of hotfix notes. It's no surprise that it went largely unnoticed, since most all of the abilities with actual breakpoints going from 14->15 are things with very minor impact (Protectors' Shadow Word: Bane, Nazgrim's Bonecracker, Hisek's Multi-Shot, etc.). There are indeed a couple of more impactful breakpoints on Garrosh's Touch of Y'Shaarj and Sha of Pride's Imprison, but those both occur at raid sizes well above 14, and randomization isn't the correct solution to either.
The 14-player "magic number" is actually a fairly interesting social dynamic, since there never was anything particularly special about the number, and now there really is objectively no advantage. As we've said in the past, there's certainly nothing wrong with wanting to form a 14-player raid, but if you're turning away strong players or friends because you're convinced that your raid as a whole will have a harder time, you're making a mistake.
Ion's point about social dynamic is interesting. The hotfix list elucidates just how many abilities weren't affected by scaling, and even the ones listed are relatively minor. For some reason, relating to the abilities that were relevant to the numbers started some sort of domino effect that escalated into players being convinced that bringing just one more person would tip the balance against them. As Ion's mentioned before
, it's just not the case.