I see. So victory for the side with 90% or better chances is assured, but nothing else is. There can be a 3% chance (according to the system you're using) of only one victor being left (let's say you attack a strong stack with two Light Infantry and kill all but 1 unit), and that can actually occur randomly.
That is not what KGB originally described. He said that the outcomes in the 10% range were removed, leaving the middle 80%. My understanding of statistics isn't top-notch, but I think that's a gross misstatement. As described, the range of battles removed as "x" would be stated:
0%>x<10%
And only in favor of the victor. So you will see someone get a highly unlikely outcome such as annihilating a stack he barely had a chance of beating with few or no losses. I'd much rather see the system implemented as KGB described with 10% at each end of the scale invalidated. Anything in the range of likelihood from 0% to 10% would be thrown out. That would be much more balanced. In fact, it would remove almost all balance issues. It would make the likelihood of losing a battle where you had 88% chance of victory (according to the simulator) approximately 2*5/4=2.5%. Gone would be battles where you have a reasonable expectation of 3-5 of your troops remaining and you're left with a hero alone. Sure, the 10% rule protected me from losing the 92% chance battle I just fought against Negern's hero, but it does not protect me (or him; making me pay for the victory is important too) from BS results well under 10% likelihood.
Outcomes of even the smallest possible likelihood are currently still allowed; the only absolute factor is victory for the side with 90% chance taken from trial battles. I was going to ask why the battle simulator would return results like 51.7% chance of victory in an even fight, but that is obvious now given that it's a trial-and-error system. Thanks for the info. Please consider actually removing all outcomes under 10% likelihood. It needs some tinkering, but I would suggest measuring cumulative likelihood for HP losses exceeding said threshold and HP losses below it. So you would not see outrageous outcomes for either side in any battle.