Like the above poster mentioned, you should really try and get some help from an FC/LS member or shout in Rev Toll. I've found, in general, that players are less likely to bail after one wipe if it's a premade group. Furthermore, although 90 min is plenty of time to clear the dungeon, you can discuss final boss strategy prior to queueing to ensure players are reasonably ready to take down that boss in premades without wasting dungeon time.