My take away is that the high ground rule only makes sense when you consider the lack of a cover system. - 5th ed has 1/2 cover, 3/4 cover, and full cover. - BG3 does not have the cover system but the High Ground sort simulates it for ranged attacks.
My feelings: - please add the cover system updated for 3d environments (will need to cast more than 4 rays) - reduce the high ground bonus to +1 or +2 to hit. (and no low ground penalty because cover has you covered now) - add in the optional flank rules from DMG (2+ characters on each side of the target) with a +2 hit only. (melee needs fun rules too)