I'm in the camp that height advantage = dice advantage is too much, but equating this to the 9th level Foresight spell is a pretty disingenuous argument and actually weakens the good arguments made here in this thread.
Just having a 8 hour non-concentration advantage to saving throws (far rarer than attack advantage), ability checks (fantastic for shove, grapple, dispel magic and counter spell), and not being able to be surprised is powerful enough for a decently high level spell.
Maintaining a high-ground advantage is also far more difficult than the attack/defense advantage granted by Foresight.
In many cases, enemy movement can simply deny your high-ground advantage by closing the gap to threaten you. A single casting of Misty Step basically guarantees it. If the AI was smart enough, it can even deny you line of sight to render your high ground useless. It's still overtuned and should be changed due to other reasons, and because the AI isn't clever enough to deal with it, but it's not Foresight.
I assume our ultimate goal here is for Larian to actually listen and apply this feedback. I don't think hyperbole is going to help that.
I agree foresight is better overall (particularly late game and out of combat), but I'm not convinced that makes the comparison unfair, particularly in a lot of early fights where all you have are really attack rolls, and when we are just talking about combat applications. There have been better, longer discussions about all the weaker abilities that high ground and back stab completely invalidate too, but I don't think it would contribute much to bring them all up here when foresight is just as useful a comparison.
Also, it's not at all difficult to maintain high ground in most fights, particularly with how strong shove is. Enemy uses an ability to get to where you are, you just shove them off the cliff or ledge, it actually makes them trying to get to you a worse move than just trying to find somewhere safe-ish and shooting from the ground. You can regularly just park your whole team on high ground and be untouchable, wizards being able to nova every single fight means your damage isn't really a big concern, and there's zero risk to it because your melee characters can launch people who try to force you off.
You can still fail to maintain it, but you have to screw up in so many different ways for that to be the case, hence my comparison to a DC5 check. Comparison to it being like us getting power word kill for a persuasion check is similarly valid too, because most of the power of that spell isn't actually relevant here either. You could kill enemies instantly with disintegrate too, but I think it makes a point to use a stronger one.
