Best thing to do with situation like this if it is a story quest and there are new players disable Cut-Scence Skipping. Also add a forced level Cap of Level 50 IL50 to those 2 story dungeons. If you bail out in the run you are automatically locked out of all instances, raids and trials for 6 hours, people would think twice about doing it. All members helping the new members would get 300% more tombs for helping out new players.