Glitching should definitely be dealt with but tank pull/raise isn't anything outside the normal game mechanics so that should be left alone, and if it's something they want to avoid in future then they only need to make dungeons with lots of locked doors/magical barriers to stop people avoiding the trash.

Alternatively - make trash worth killing! A chance of a good item drop or simply worthwhile gil would do wonders; or if that's too much why not cut the trash out altogether and have a boss rush dungeon or one that's full of tricks and traps instead?