I think some people misunderstand the entire point of "roulettes".

The point of them (by design) is to fill the gaps in duty queues. If a healer and 2x DPS queue into -somerandomdungeon- but no tanks want to do the dungeon for 3 months, then they are stuck in queue for 3 months (an exaggeration of course, but I believe it was needed to get the point across). A roulette fills in that gap by offering the tank more rewards for clicking the "I don't care what dungeon I do" button.

If you want the bonus from a roulette, you have to accept that it may or may not be a duty that you were hoping for, as you will get the dungeon that's currently "in demand", so no it's not some bug - it's just in demand at the moment (as others have said, due to current Eso farm). If you don't want to do a dungeon in the roulette list, then maybe you should just queue up for -someotherdungeon- that you actually want to do, and accept that you won't get as high a reward?