well this is helping me and i want to share.
i just tell me friend stay way from me every time i see a boss quest and i take the quest, he could be able to move and you too.
consider the distance, it should be enough you should not see your friend but don’t stay too far away because you could not go in to kill the boss
but this still a problem because when you are taking a new quest and you are a new player you don’t know if you going to fight a boss or you will see a cinematic but still this is helping me a little.
if you have another solution please post it.