Qarn today had Sastasha the last two days in a row there really is no real pattern to any roulette you just need to be prepared to enter any of the dungeons on the list and not whichever one you'd rather do. I'm not really sure how the DF handles it if there are multiple runs with an open slow for all three if it just picks one randomly or it puts you into the one waiting for the longest time. The latter does make sense. Getting the same dungeon multiple days in a row is just being unlucky with RNG but there are only 3 dungeons in this roulette so there is a 1 in 3 chance of getting whichever one you like the least. Sastasha isn't really that bad except for a last boss that drags on or if you get a new DRG that instead of stunning the tail whip runs around in circles >.>.