Good spirit to the idea but way over board on the implementation. T11? Seriously?
Tiers 1-3 are pretty much ignored/garbage (other than giant/dragon, more on this) because BoE gear is significantly better and, in the absence of ringers, easier to obtain. Completely remove these tiers from the 18 man game, which has the nice added bonus of making the number of tiers a nice even 10 + crank it to 11 for two fights. Since that content already exists put it to good use being actually useful to new players by:
All the one shot mobs (Gnok, Lenny, etc...) >>> Become adepts lvl 55-59
This would be a boon to the perma 55 game as well as for players passing through this range (read: everyone at some point). The drops could, for the most part, remain unchanged AND be made xpable without anything unbalanced happening.
Halls of Misery, Dreadfang >>> make 6 man
Some tweaking here and there. Having more 6 man zones would be good for people who want to play regularly but cannot commit to raiding for one reason or another.
The really low tier plane fights >>> ...make them harder?
Or just call them the new tier 1 and they'll be easy fights. That was easy.
Dragon/Giants >>> leave NDHK, SE, and Rymaz as low tier raid targets and make the rest 6 or 12 man
Either would be good but having an "intro to raiding" with low level 12 man raids might be something that appeals to people or eases them into raiding or makes them eat lots of pistachios then feel sick and get drunk on pain medicine only to call their ex at 2am singing Foreigner. People, go figure.