The problem is tanks fishing for an in-progress run. SE's dungeon finder is literally the worst system I have ever seen. No other game does this - one tried, saw how fail it was and immediately patched it - but in XIV it persists.

The way to solve this is remove the "Join Party in Progress". Everyone gets filtered into dungeons as slots open up, in-progress run or not. No one can see how many bosses are dead. You want a full run? Queue up the dungeon by itself.

And then fix the design of the dungeons so they don't take 30 minutes to an hour. That's too long for a 5 man dungeon, nevermind a 4 man dungeon. 15-20 minutes is about right for fresh 50 dungeon roulette content. Raids should be long, 4 mans should not.