Downloading as we speak the latest version.

Figure out my tests are done with Shimazu on Hard short campaign and I have no other mods but yours.
I would like to know the list of the mods you are using so I can install them and test the same game you have.

Take into account the importance of making the AI vassalize more in view of trade, treasons and the implied intervention of the main clan if the vassal is attacked. After merely 15 yrs of war there's just really 5 or 6 major clans on the map in 1.95 and that's not good (though it's almost NEVER the same clans). It is likely that if the AI takes care of defense before attacking someone else it will be harder to wipe out a faction, any faction, and the minor clans should do the somersaults to ally to their most powerful neighbors (you mess with me, you'll mess with the big boy behind me too!). I think it's a matter of logics more than DB. You can buff a faction but if its home castle is destroyed because it is left ungarrisoned that won't save that faction.

If you can really take care of these 2 things, everything will go better.

As of the Exp points, look at the archery dojo. The sam unit is already better than the ashi unit but also starts with more XP. Basically, an overall decrease of the starting XP points should keep things balanced and they will remain balanced if units are removed from the game once they reach 66% losses (with less than that the player is still forced to keep them behind to replenish otherwise they will be lost so it's very good you decreased the replenishment rates).

So in summary, imho the priorities should go to siege/sally credible % of success before enterprising the action, diplomacy more vassalization (losing AI clan should offer to be vassal to winning AI clan and winning AI clan should accept more often because a vassal is less threatening to the other clans than that faction conquering the whole Japan), more alliances, better understanding of the importance of garrisoning the castles: you can't attack if your very existence as clan is in danger.