When I first started playing I really didn't know what to think simply because I didn't know much. I didn't have clear expectations. I joined late HW and played SCH up until around Lakshmi before I started maining DRG. I still preferred larger pulls back then but couldn't really give any opinions on anything because I didn't know enough. I only really knew SCH and DRG, that was it.

Nowadays my expectations are far higher and it does help that I have a sturdy understanding of most jobs in the game. I expect significantly more from players that have other jobs at 80, especially other jobs within the same role. Most of my expectations come from, similar to the OP, that most of the jobs/roles have been simplified significantly and made far more accessible. I expect players with more play time to be able to carry their weight at a bare minimum. Please keep in mind I'm talking about 71+ content, as lower level content is very different.

Tanks I expect big pulls most of the time. With how many additional strong cooldowns have been added to the game (Arms Length, Reprisal) there should rarely be an issue with taking damage to the point that it becomes overwhelming, especially considering some tanks (DRK, WAR at 76+) are incredibly powerful in dungeons and should almost never die. Tank stance no longer contributes to damage or defense so that's completely free now. Positioning... I'd just hope tanks understand enough to keep the boss more or less in one spot and not continuously rotate the boss. If they have other jobs at 80, god forbid other melee DPS, I expect this even more.

Healers are far more accessible this expansion (not in a good way, in my opinion). The topic of "Healers should DPS" isn't even a question to me, I expect healers to use DoTs at a MINIMUM regardless of experience in all content, and that's something I'll regularly comment on if i see healers not doing that.

DPS I only ask that I don't carry the damage contribution in the group. DPS I generally have the most gripes with in Duty Finder, especially in leveling dungeons because so often I see them not using their full kit remotely. I've lost count of the amount of times I've had BRDs that don't use songs at all (I got in an argument with one at 75 two days ago), or people just not using AoE skills. I shouldn't have to tell people when they should be AoEing... and don't get me started on players who have other DPS at 80 meanwhile I do double their damage on NIN........ Oh, and ranged physical/casters being in Narnia while I try to heal on AST.

Leveling dungeons frustrate me far more than raids ever have. It blows my mind how people think it's justifiable to queue into content with 0 knowledge of their job and literally just don't care. Leveling jobs is the sole reason why I've come to be progressively more frustrated with the community/players these days...