I'm not a DnD fan nor a DoS fan and I played lots of tactical TB game... the first playthrough was difficult to me.
I guess we have found something.
But I didn't play only DOS, for me DOS was just another isometry game after PoE. So I don't know, in DOS for me main difference was tactical pause, not fight difficulty.
The most difficult fight in BG3 for me was spider, because "bonuses" don't work. There is a specific mechanic with web and strategy with destruction of eggs. In theory, you can push a spider into a hole (I didn't know this first time), but it doesn't give a 100% guarantee, especially after patch 3. But it's boss so... It's fine. I mean, I think it should be difficult.