I've recently finished work on a mod that reduces the power of agents (particularly AI ones), by targeting the ability for them to successfully attack the same army or settlement turn after turn.
The 'On Guard' buff's duration has been upped so that it actually works against the AI.
Settlements now gain a defensive boost after an enemy succeeds against them.
Agents are now 'Fatigued' after succeeding against an army, settlement, or character, reducing their chance to succeed in subsequent turns.
The side effects of these are that the AI agents will level more slowly (thanks to less successes) and agents are now incentivized to pick new targets, instead of hovering around the exact same one.
I have not edited any agents base success chance, nor the power of skills. I do have another mod that stops agents gaining hidden success chance from skill points, but it is in no way mandatory.
I have not completely eliminated the possibility for two successes to happen in a row - but it is now going to occur very rarely. The absolute best odds (on base success chances) that the same agent succeeds twice in a row is 15% (for a spy hindering an army), so now you will know that if the AI does manage it, it has got very lucky.
And that's basically it - I encourage you guys to give it a go, it is save game compatible (and I'm actively working on reducing mod conflict to as much as possible).
The Steam link is here - http://steamcommunity.com/sharedfiles/filedetails/?id=694959518
Let me know what you guys think, and enjoy the game!