I think OP is specifically talking about tanks or healers? Because that's one of the reasons why no one goes tank or healer for the most part. If a DPS leaves who cares? you still can DPS a boss so long as you follow the mechanics, but if the TANK leaves then the entire party is at a stand still with just trash. So if you put a bigger timer on these needed classes than that would further discourage tanks and healers to run dungeons or pick up the class in general. As a tank I am nervous going into any dungeon at any time because something could happen at any given time where I must leave (especially since I am a parent), but I love being a Dark Knight. I feel like the penalty is fine at 30 mins, but I think it should increase with consecutive abandons until the next reset day.