Roulettes in general need more options, not fewer. (The only removal I'd be behind is the removal of EX trials from mentor roulette; they either belong in their own roulette or not at all.)

Level 80 roulette right now is going to be weighted heavily toward Amaurot because it's the only dungeon in the bunch required for story.

In general though, if the 80 roulette has a "1/3" chance of giving you a dungeon you don't want to run, you might be best off simply not running that roulette.