Some thoughts on unit sizes

[Puzz3D]

You're assuming that it's an absolute difference that matters, and not a relative difference, or do you have evidence that it isn't?

Yes. The designer gave us the combat formula for STW and MTW, and it's similar for RTW eventhough they won't reveal the exact formula.

For STW and MTW:
chance to kill = 1.9% * 1.2 ** (df)
df = (attack - defend + bonus)

attack, defend and bonus are all integers to simplify computation.
attack is the striker's attack value.
defend is the target's defend value.
bonus is any situational combat modifier that applies.
df is limited to a range -x < df < x
x is 20 for STW and MTW, but most likely a larger number for RTW since the 1.2 constant is closer to 1.1 in RTW according to my tests.
lethality in RTW is a new parameter that most likely comes in as an additional multiplier.

they would have to do somethign to get around the divide by zero issue - maybe that is why the minium defenseive value is zero

Is the minimum defensive value zero? Both attack and defend values could be negative in STW and MTW, but I haven't tested that in RTW.