In Diablo 3, my character's progression is tied very tightly with the questing system. This makes it extremely difficult to play with friends who are even around the same level.
In Diablo 2, only one or two quests per act were required, so if a friend fell behind or I fell behind a friend in progression - we could just finish the act in one quest and I could rapidly catch up. In Diablo 3 this doesn't seem possible.
If I want to play with a friend who isn't at a 1 to 1 progression of where I am at on my quests, the only way I can play is for me to go back to previous quests and start from where he is; or my friend comes back to where I am on my quests. This makes it extremely slow to progress through the game if you're playing with different friends.
After I've seen the story once on normal, I am perfectly fine with skipping some parts of the story in the name of progression for higher difficulties and new characters. My question is, what strategies exist to play with friends who are not on the same quest as you while not gimping your progression through the game?