No...you don't have to "carry" the other 7 characters to hell at all. You can have them spectate your main character from act 1 killing baal in normal and nightmare, and move them all into hell within the span of about 5 mins or less. What exactly are you running in the span of 2-3 min that requires you to have 8 players in the game by the way? The boss drops are fixed to always drop well regardless of the number of players in game. The only time you need players 8 is when you are running maps or vanilla content, and you can open multiple maps in the same game. Most of the time, the game timer expires on me around the 3 hour or so mark because i just keep running maps in the same game. I only have to make all the characters join a new game maybe 4 times day.