So one of the major problems in WoW has nothing to do with game mechanics, classes being over or under powered, abilities that don't work correctly or the idea of 10 or 25 man raiding. So I know you are asking, what is it? Simple, have you ever noticed that everyone looks the same? Yes the problem with WoW is as everyone gears up everyone looks the same. Horde, Alliance, race whatever. There is no way to define the individual. Sure we have the barber shop where you can change the way your character can look, but that doesn't really solve the problem. So what can be done about this? Well it really is a rather simple solution. In other games they have the option of changing the tint or colour of armor sets and this would be a great start for people being more original and finally you could tell the difference between people who have similar gear.
So as this would be a start I have something else to propose. Why not have the option of wearing completed sets you have used in the past. Blizzard has some great artists who have done great work on tier sets, so why not put them to use. So as am example I love the way Warrior Tier 6 looks I would make myself look like that while still wearing the current tier set. People would see a warrior in this gear with the colour I chose then they would know it was me. This not only promotes originality, but also would get players going back into old content and not having it all go to waste. I guess you could apply this to some of the collector outfits as well, such as the Twill. I don't think this should apply to weapons just because of animations and such, but that is just my opinion.
Sound like a good answer to the problem?