A warlock player by the name of RaChoMoy. The player was in a party for an instance run, Old Glast Helm Hard. Difficult as it is and the type of party we have. The party require all players to pitch in.
At the final boss, veteran players who had done the instance before warn all party members to not melee or use magic. Despite the warning RaChoMoy, continue to insist of using magic throughout the battle. Resulting multiple party wipes and making the completion of the instance difficult.
See screen shots of the player casting magic. Unfortunately, there are no screenshots to give further details because we were all trying to survive with the ignorant player. Some indications are in the text, actions, and way the other party members are position (spread out)
If any other members were part of the party, feel free to comment or add additional information.