It seems you made dungeons entrance and matchmaking via fixed places on particular maps. Constant backtracking to these places is annoying, waste of time, and serves as negative experience.
Suggestion: apply system via which player can queue into any dungeon/mission at any moment in any place. For example, TERA Online has such a system.
You already have a template /indung. You can link to each dungeon/mission name there a queue system, for example.