We tried running a mission together with one char of lvl 130 and one char of lvl 127. Both have access to all areas and such. It is not possible. We always get the message that an instance is already active and there can't be another instance. No matter which char is group leader or the first to enter the mission.
Running missions with a friend and having an alternative leveling route was one reason to buy this "mini-expansion". If you always have to be of the same level to play together a mission that is not quite possible.
Quite dissappointing. With this limitation there is also no sense in buying this "mini-expansion" for another account.
"...In the information society, nobody thinks. We expected to banish paper, but we actually banished thought."
Ian Malcolm
From: Crichton, Michael. Jurassic Park