Why just not set a limit on high ilvl you can be the first two weeks of a mythic raid release. Make it slightly higher the second week than the first tho. The point to farm heroic raids endlessly to get better gear is removed and everyone or at least the top guilds will be on a equal playing field. This wouldn't affect most "normal" guilds since those guilds wouldn't even hit the ilvl roof.
This could obviously be tweaked, but i think that this would be a better option than to remove master loot since this change would mostly affect those at the very top anyway.
So what do you think, Y/N?