I greatly enjoy the timer honestly, it adds a level of tension and importance to keeping a decent pace in a dungeon not to mention the importance of the task in general for whatever reason. lore, objective, ect.

But i also agree the timer should be extended if a player drops when a new one is added even if only by an average rate say... 10-15 minutes? That's at least a boss worth + trash clearing. Maybe a 5 minute timer boost for clearing a boss first try or something?