For the love of everything good, please use the mic if you are going to do any type of group activity. Dungeon, trial, whatever.
Sorry, but it's getting annoying that people randomly join dungeons, then run ahead into the mobs without warning, then stop to rifle through their bags, then run back to get a quest marker they missed, then run ahead again....all the while not ever getting on the mic to reply when then rest of the group is politely asking "Uh, what are you doing? Hello? HELLO??"
The mic (or text when that arrives) is necessary for basic group communication. USE IT!