It's simple, there should be LFR(looking for raid) which is the easiest difficulty, Normal which is normal and Herioc which is the hardest. LFR is for the whining ppl who want matchmaking for raids but they don't get good gear really. Each difficulty would have a different colour raid set and it would mean something if someone would have heroic gear. To get to normal you would have to have LFR gear and to get to heroic you would need normal gear.