The people who are getting attacked, are you having non-stealthy units in the group being attacked?
No my last game game I lost single 4 single unit armies that were nothing but Scout units with Weak, Explorer and Stealthy.
Maybe the whole group has to have the stealthy trait in order for it to work?
If you have a bunch of Aragorns and Legolas's moving through the wilderness and one Willie Sanderson along with them, it would make sense to me that the enemies would be able to detect Willie Sanderson and immediately want to smash him into paste regardless of the fact that he was surrounded by people that are otherwise stealthy.
Ok, this made me chuckle but to avoid having the thread derailed it probably is not a good pointing fingers at a specific person on the forums. Although, Willie is very negative he does make a few good points in some of his posts. They might need to be rephrased a little bit.
Side Note: Can the weak unit trait be added back into the base game. For balance reasons reducing -1 tactical movement, 8 init penalty, -2 attack should make it unattractive enough to not be exploited. I like having really cheap scouts for exploring the map. Otherwise, I might just play around with the XML.