This was in part due to the nature of LFR. The only way to raid LFR level content is to queue for it through the raid finder interface -- you can't simply change the dropdown difficulty on a per-character basis, as you can with Normal and Heroic difficulties. Once you've passed the level threshold for Cataclysm content, the option to raid Dragon Soul LFR simply disappears from the raid finder interface. Ordinarily this wouldn't be a problem -- but transmogrification addicts everywhere have been looking for a solution to obtaining those older, uniquely colored items, and Lead Game Designer Ion "Watcher" Hazzikostas just tweeted that a solution may be on the way in patch 6.0.
@Arisoh1 Yes, hoping to add an NPC in 6.0 that will let you enter Dragon Soul LFR in a private group of any size.- Watcher (@WatcherDev) March 29, 2014
This news was unexpected, to say the least. While it's not a confirmation that the option will absolutely be added in 6.0, it does point to the fact that Blizzard is at the very least thinking about the issue and how to offer an alternative solution. Transmogrification has been a wildly popular feature ever since its introduction in Cataclysm, one that has actively encouraged players to go back and run old dungeons and raids in search of the perfect armor sets for their characters. With Warlords of Draenor sending us all to level 100, hopefully we'll see this feature added for Mists of Pandaria raids at some point as well. Until then, if you're looking for LFR color schemes from Mists raids, you may want to hang onto them once they're in your possession.