Silly question. Using an old character, world hopping and websites to look up your map can make this super cheese. Rather the shortest time is likely to be the biggest cheese of all.

If you are playing to beat the bosses the fastest then you are playing the game wrong.

You could probably do it in less than an hour if you joined a server with everything done. Just equip stuff others made and farmed and go kill the bosses one by one... then call yourself a hero ha ha ha Heck you could probably do it in half an hour.