I've noticed that a class restriction has been put in place recently for the T3 in the store. This however shouldn't be, as they do not have a class restriction, nor had it ever been added in the later expansions. In fact, with the addition of the BMAH, everyone can obtain them for any class, as evidenced here: http://www.wowhead.com/transmog-set=...egear#comments (The only limitation of usefulness was the armor-class transmog restriction, ie the plate sets would've only been useful for that purpose for Paladins, Warriors and Death Knights)
Could you please consider lifting this restriction?
The reason these items do not have class restrictions is because they were quest rewards. The quests themselves were class specific. These item sets were either extremely rare on the relevant classes prior to MoP due to being unavailable during WotLK and Cata, or extremely rare on any class on MoP or beyond due to the black market AH. Due to these things, the restrictions that we've put in place are very unlikely to be removed.
It's a wonder that they're even in the WotLK marketplace in the first place, since they are otherwise unobtainable.
There are a lot of things that are 'otherwise unobtainable' on the marketplace, actually (mounts and pets, just to name a few) which are reasonably irrelevant (mostly cosmetics in any case), so theres that.