What about a completely radical break from attunements at all, and have different server levels?
Think Diablo. Normal, Nightmare, Hell.
Normal, "standard" wow. Most players
Nightmare - Transfer here if you want to play more challenging - same server size, fewer of these though. Things like the ICC buff occur far slower.
Hell - The best of the best - Transfer here if you're in a guild that guns for server firsts and/or world first. Maybe only 1 server per continent.
You'd have to prove yourself all over again if you moved from Normal to Nightmare and again from Nightmare to Hell, but at the same time, those on the more difficult servers would know that you are serious in your intent to raid, rather than wanting it handed to you.
A) Server transfer charges would prefferablly be dropped for these moves.
B) Removing the top 10% of players from each realm would probably exacerbate problems and make it more difficult for newer players to not learn bad habits.
C) A true 'caste' system would be created
D) It would be difficult to establish yourself on the next tier
However this would allow people who are dedicated to progressing and are serious about wanting to improve to find that path.
Maybe this has been discussed before and rejected, but it would seem to resolve the core, underlying problem, dedicated players wanting a way to remove a lot of the crap without hindering players new to the game who would advance to that point and join them.