If you were to read MMO or Official forums, there is a voice among the playerbase that wishes that the color still meant something. Now, I did not play in Vanilla or TBC so I cannot speak from first hand experience, unfortunately. But the overwhelming majority of my WoW friends have been playing since launch and they have all shared these sentiments: Purple used to mean something spectacular.
I've heard stories of players in full T2 from BWL standing in Stormwind getting tells from players in awe of their epic raid gear. They were overwhelmed with excitement, envy and a love for the game when they saw another players accomplishment that took months to obtain. There was a seemingly insurmountable power curve to the raids in Vanilla that REQUIRED completion of ALL raid content before proceeding to the next tier of raiding. Raiding content was so difficult that new tiers of content was released prior to a world first kill from the previous tier.
These things, when compared with the current iteration of WoW are difficult to believe! I am in no way saying that in order for WoW to be a great success (it is) it has to regress into a previous state of the game. Only proposing that if some of the heroism and grandeur that was present in the game so long ago were to be re-introduced in some fashion, the game as a whole would benefit.
Prior to badge gear, valor gear, timeless gear, apexis gear, and Garrison mission cache's the only way one obtained epic quality gear was through raiding. My proposal is to return to that model. Retain those mediums of obtaining gear, but make them less lucrative in the grander view of the game. Really and truly provide incentives to progressing through raid content. Restore that overwhelming elation and sense of awe to being in FULL epics again and make it really matter. Because in the current stasis that the game is in, it is void of REAL accomplishment, merely repeating the same content again and again through 4 difficulties. If you're going to keep the multiple tiers of difficulty, at least make the gear you acquire TRULY epic.