I don't particularly mind that the Crystal Tower is faster or easier than later raids. I probably also wouldn't mind if there was a tighter IL sync on Labyrinth and Syrcus Tower. However, even with a tighter sync in place, it would still be possible to cheese the roulette simply by not unlocking any other raids. With that in mind, I would prefer it if the roulette requirements scaled with level such that you can only queue for the roulette if you've unlocked at least the first raid of each cap level your current job has met; with a minIL of the highest raid available to that job. Some discrete examples:
Ex. 1:
Your current job is Lv60 to Lv69. The roulette should require both Labyrinth of the Ancients and Void Ark unlocked and your minIL for queue should be 175, the minIL for Void Ark.
Ex. 2:
Your current job is Lv60 to Lv69 and you have unlocked the Weeping City of Mhach. Your minIL for queue should be 205, the minIL for Weeping City.
Ex. 3:
Your current job is Lv80 to Lv89. The roulette should require that you have unlocked Labyrinth of the Ancients, Void Ark, Rabanastre, and Copied Factory, with minIL 435.
People will complain about being locked out of their roulette every time they reach a new cap level, but honestly, so what. People already get locked out of DR:Expert whenever a new patch comes out until they finish the new dungeons and meet a higher IL. It's not a huge burden to require people to unlock a single raid once for each cap level to maintain access to DR:AllianceRaids for all current and future jobs.