The problem is not the advantage gained by height. Its the ability to jump several yards in full armor, weapons and backpack from the stand like super Mario. Remove that and shove entirely and height advantage is harder to get and balanced then.
I am not so sure about that.
Jump should cost movement, not an action or bonus action. And shove should also cost an action.
Advantage (in the sense of DnD 5e rules) is simply too strong, even more so when the enemy on the lower ground gets Disadvantage as well. It's waaaay too much! Larian should just remove that mechanic of Advantage/Disadvantage by height alltogether. If they want to somehow give you an advantage (NOT Advantage as in DnD 5e rules), a simple +1 or +2 Bonus to your attack roll is more than enough.