SE you should not penalize your players for withdrawing or missing a queue. It is very unnecessary and turns off players. The penalty for being afk should be you missed your queue and have to wait again. You should use the system that Blizzard uses in wow its very similar to the frontlines system that is already in place in FFXIV.

Everyone who hit commence is enters in the dungeon no matter what. Say if you had 22/24 on CT, 1 person withdrew and 1 was afk. Those 22 people are sent in the zone and the 2 are filled with the in progress feature which you make mandatory like frontlines. There problem solved with little or no penalties.