Since it seems like we won't be getting any retro-active DXP (I can understand why they did it) I was wondering has anyone found a star cluster with a higher percentage of non-combat missions than another?
No, they're about all the same from each other. (Unless ya come across a bugged Diplomatic Investigation mission, that keeps repeating over ad infinitum, like I've been getting in Arucanis Arm Cluster. A rare helpful bug to be sure. ;P )