The better option would be to just increase the flat odds. DQM: The Dark Prince is brutal with it's odds, but fair. A 45% chance is 45%.

In games like Civ/EU/Stellaris/Sins/etc It makes sense that a 3:1 battle wouldn't scale linearly, especially if you have higher morale/tech/etc. Bullets have a miss ratio, 3x as many bullets at the same target narrows that gap and gives the larger side an advantage at more quickly destroying the other side. So just give it an oversized ratio to scale the base (1:1) odds at.

That keeps "losing" realistic...a once in an occasion happenstance of luck/bad tactics/etc but also a generally very favorable and reliable outcome for your side.