Hi I've been enjoying your mod for quite some time now and wanted to say thank you very much.
I had a changes that I've done w/assassins in my own game that you might want to consider:
In the descr_campaign_db
This rule deals with the multiplier given to assassins trying to kill someone in their own territory. The default value is 0.7 meaning that you get a 30% penalty for trying to kill someone in your own lands.<assassinate_own_region_modifier float="1.05"/>
Changing it to 1.05 makes it much easier to kill low level priests and merchants and cuts down heavily on the "spam" aspect cpu's might use.
I still haven't found which rules deal with whether an assassin dies or not after a failed mission but I think that the general rule of thumbs for making assassin values should be that they should have a low chance of survival if they fail (thus making you much more discriminative in choosing who you assassinate and not going on an unrealistic assassin rampage).
A well trained up assassin who has a fair chance of killing a leader should probably be expected to die if he fails. Just my two thoughts. Thanks