@mg666 yes, this is exactly what I was showing! I argue that "relative difference" is a more useful number than "absolute difference", and using this method leads to the conclusion that Advantage makes you succeed 50% more often on average.
(I assume you were referring to my slight miscalculations involving needing a 5/15? If so, corrected)

Originally Posted by SacredWitness
Correct. It's not a flat boost. It's a bell curve based on target and difference in roll. *snip* The flat boost option is there for people who really don't want to trust the die.

It's your latter sentence I want to emphasize.
If Larian wants to remove/reduce RNG-frustration, then changing height/backstab Adv/Disadv to a flat (+2 hopefully. I'd settle for a +4) boost would be better than advantage. It also neatly solves the issue of height/backstab advantage interfering with standard 5e abilities/spells.
IN ADDITION, this allows for easy creation of different difficulty levels. Story? Height for player gives +6 bonus to hit. Easy? +4. Normal? +2 Hard? no bonus