What is the Courtesy Move here?

I am looking for peoples opinions here. which of the 2 options is the courteous solution:

1. when running dungeons with one of the super fast descendants should you be the one running them solo?
2. when running a normal speed descendant should you be the one running the dungeons solo?

I ask because of the frustration when someone super speedy gets to the boss room and just charges in forcing the teleport to the boss room which removes all the buffs the other descnedants have been building up, and also prevents those with out fellows from collecting loot. so 1 or 2 which has the responsibility to be courteous and maybe just run solo?