It's always that darn dungeon..

[GrizzlyTank]

Probably just confirmation bias. Because you dislike that specific dungeon, you are more likely to remember/note whenever you get it.

[LisSquid]

Probably just confirmation bias. Because you dislike that specific dungeon, you are more likely to remember/note whenever you get it.

You seem stuck in the no-fun-allowed dungeon.

[Iscah]

Probably just confirmation bias. Because you dislike that specific dungeon, you are more likely to remember/note whenever you get it.

There'll be some degree of that, but it's also not an even chance because it hinges on what dungeons are available to every person in the party. (Apparently the system groups you up and then looks at what you're eligible for.)

Barring a short period if you set about unlocking optional dungeons soon after reaching post-ARR, every person participating in 50/60/70 has done Snowcloak and Keeper of the Lake via MSQ while everything else at level 50 is optional. If one person in your group has ignored sidequests and is levelling a class under 60, those are your only two possible options. Once they get to 60, you add in the ARF, Antitower and Xelphatol but that's still a 40% chance of getting those early dungeons.

If one person in your party is a thorough unlocker of sidequests who has all the level 50 dungeons but is under level 60, and another person is charging through the MSQ and is 70+ without a single side dungeon unlocked, the intersection of those two selections that everyone is eligible to play comes down to, once again, Snowcloak and Keeper of the Lake. Possibly not even Keeper, if the thorough person (or anyone with Snowcloak and a single side dungeon, and thus eligibility for the roulette) hasn't gotten that far yet.

The system is definitely, inescapably rigged to favour certain dungeons because of how the variables interact. Even if you have four people at 70+ with everything unlocked, you could still get Snowcloak, but your ragtag group with under-60s is never going to randomly get the Ghimlyt Dark.

All that said, I do agree with Reiner's observation that DPS seem more likely to get pulled into high-level and/or optional content while tanks and healers get MSQ duties. I assume it's because everyone comes up against MSQ so there's an excess of DPS queuing for these (on top of the "rigging" effect) while people that are actively trying to queue for duties are more likely to pull out their tank or healer classes to hopefully get in faster. I also find that high-level DPS have a chance to jump the last bit of queue since we might get plucked out for a spot in a high-level dungeon that nobody ahead of us can fill.

Ultimately the biggest way to get more variety in these roulettes is to encourage people to unlock the optional things, preferably as they go along, so more people in the roulette have a wide variety of choices. It also means roulettes like trials, raids and 50/60/70 are quicker as having those things unlocked means you might get picked out to help someone queuing specifically for that content.