I will definately try patch 3 tonight, (if i understand corectly you run the patch 3) and then restart my Parthia campaign to compare the two versions.
In the campaign i completed, no body backstabed me, and all the agents were just walking by my teritories, as well as their armies, standing besides my settlements doing nothing.
I just didnt bother with them.

When in war, there were times, that the enemy agents imobilized my army but that was all, no enemy army was exploiting the situation.