A party member in an dungeon instance joins and then AFKs for the rest of the dungeon. I don't see this often, but when it does occur it can be rather inconvenient when the AFK member is the party leader. Whether or not if this player is leeching on purpose or not is another matter.

When one person happens to drop, then there is no possible way to replenish ranks, as the AFK leader holds the sole responsibility for this option.

There isn't any way to kick an AFK party member in a dungeon instance, nor does the game even uses the idle kick feature to remove players abusing this in dungeons.

Is the only option is to report the player and hope that someone might remove the player?
Would the GMs even take any actions towards this behavior?
Is this issue even on any list of concerns?