Here is what I do, and it works.
DON"T leave group. Just sign on out 4 guys. One guy has to stay for little.

When they sign out, they end up at the start of their own fresh instance. Now sign in on 1 or all of them again. THey will be back at the start. Walk them outside instance.

When they are outside, have person left inside at end, invite one or all of them. After they are in the group, have 1 of them walk in (just need 1 person). They will be at the start of a mostly finished instance. There will be respawn, so it will look new, but it is the one that the person at the end is in.


Then have the person at the end logout. Not leave group, just logout. He will end up at the start of the instance, just like the others did.

Sign in on that last guy. Have everyone walk outside isntance. BAM. All at same place, and no respawns. Yeah, it is complicated, but MUCH easier than fighting respawn. If you leave the last guy signed out even when he is at the end of the isntance, he will end up at the start after about 1 hour. Just incase you are too lazy to switch people out or you are done for the day.