The only leniency I think should be adjusted should revolve around the time it took to get into a dungeon. As a higher level DPS, I sometimes have to wait upwards 30-45 minutes just to get into a dungeon. That makes leaving not really an option, since it's a roll of the dice for the next party. I think the leaving in a dungeon should be higher so those healers and tanks that say "Well, I can just insta-que once the penalty is lifted" actually have to think twice about possibly screwing over those people they're leaving. I've been in many instances where replacing a healer or tank either never happens, or happen after another lengthy wait time. Nothing sucks more than waiting 45 minutes to get into a dungeon, only to have to wait another 30 to replace a healer.