Reading through the solutions here I still think the best one would be to just give players some choice over what they get in the roulette, especially for alliance. We clearly have two camps, one that only wants the level 50's and one that wants anything but the level 50's. Getting the latter group to queue more solves the issue of waiting for the higher level raids.

Trying to "fix" the ilvl algorithm introduces more problems. You allow for undergeared players in content that is more challenging than most duties, encourage people to abandon more, and my own personal concern, I still won't be able to avoid the level 50 raids which makes the alliance roulette not worth running.