Be careful. From a BUSINESS STANDPOINT the one that it makes sense to get rid of is the one that's utilized the least. That would be Mythic by far, and I don't want to lose my endgame thanks.

Opening up the endgame to casuals through LFR/Normal/Heroic allowed them to justify more resources to raiding which made actual raiding (Mythic) more engaging. Don't fuck it up for yourself and Mythic raiders because you want to feel special for raiding a higher difficulty.