The problem is very straightforward, there are a lot more damage classes to level up than there are healer or tank classes, we all know that, the solution is also straightforward, increase the rewards for low level roulette. Gil and tomes just aren't enough as they are very easy to come by. My view would be to have a token system, where you recieve a special currency redeemable in the adventurers guilds for purely cosmetic items or other such goodies. These items would cost quite a bit to obtain, hence encourage people to run the instances more often, and hopefully help out the queue times for low lvl