I'm not a D&D expert by any means, but I read the OP's first post and it does correspond with alot of what I'm seeing in the game. I've got about 200 hours logged in this game so far, and the high ground is the single most powerful strategy in the game.
And it's everywhere. From the moment you encounter the hill outside the Druid Grove and snipe the goblins relentlessly below, to the rooftops of the blighted village, the high ridge in the eastern part of the goblin camp, and the ramparts outside Dror Ragzlins throne room, there is no encounter I've yet found that doesn't yield this overwhelming advantage.
Fights that your party could never win in a straight up fight are made trivial by the high ground. I have neither the experience or expertise in 5e D&D rules to speak on possible solutions to this issue in an educated manner, and I don't intend to try.
But I do recognize overwhelming strategic advantage when I see it, and in this game the high ground is it.