As we have seen with cov's, racials, and talents that customization is a bad thing in a MMo. We should be able to swap classes on the fly. Like I should be able to be a rogue for M+ but a firemage in raid without having to level up new characters.
Also blizzard stop with the different stats on gear. Just have Ilevel be the universal stat that makes you have a flat increase in damage done. Its pretty simple blizzard, why haven't you done this yet? If I want to play the must optimally for any situation you should give me the freedom to, like Preach says.