... I read through the first few pages of the thread and saw a lot of comments arguing that the advantage from height is overpowered because it's just as good as Foresight, which makes me wonder if the commenters have ever played DnD, indeed if they have ever played BG3. You still get all the same advantages from Foresight for any roll that is not a ranged attack from high ground. If you do find yourself ranged attacking from high ground, then you can do it while casting into shadows or being threatened by an attacker and still get the advantage that would otherwise have been negated. Foresight and most of the other abilities cited are still very good abilities to have.
Other than the fact that those situations are MUCH farther few and in between than "You gain Advantage when in High Ground", which is EVERYWHERE in this game. So, why is Foresight useful if you can just find High Ground and get your Advantage? It's not, because why have Foresight that gives Advantage, when there is High Ground everywhere in this game that grants Advantage.
The fact that High Ground gives Advantage, it's ALWAYS better to build a character with any inherent +bonuses instead of Spells/Abilities that give Advantage because you can so easily find it with High Ground. And, any Spell/Ability that allows you get to High Ground easier, is automatically giving you Advantage and is thus the BEST choice, all the time, instead of a utility choice.
The only time where other Advantage giving abilities are equal or better is if the map is completely flat with no way to be on High Ground. Then, your right, but Larian has already said that verticality is a major part of this game (and we can already see this in EA), so your basically saying "I am not going to be playing to any major part of this game because I want to do Foresight." Does that sound like a good design to you?
This is the problem with High Ground gains Advantage is that it nullifies so many Spells/Abilities that give Advantage and makes combat so very one dimensional, always get +bonuses along with ways to get to High Ground, never take things that just give Advantage because you can just be on High Ground and gain it. And, now combat is ONLY ever about getting High Ground. You can't take other avenues because they are so much less effective (instead of only minorly ineffective) that it makes players always play a specific way.
DnD, and thus BG3, is meant to allow for your way to play. But with something that basically forces you do play along those lines, your not allowed to play other ways unless you want your entire game unenjoyable and harsh just because your not playing the way Larian wanted you to play. This is always bad design, especially in RPG games of this nature (based on DnD).