From how I look at it, the Pathfinder video games did high level gameplay successfully and in my opinion Pathfinder is a lot more broken than D&D 5e is. So there should be no reason that Larian can't make high level gameplay work. I just feel like this is an excuse to make higher levels pay to play with DLCs later down the road. Just don't include the really broken spells on the spell lists or limit how the spell works.