Replaying BG1 and 2 now and i'm pretty sure the combat in PoE, 1 at least, is a direct evolution of that. Maybe a bit too reliant on choke points on higher difficulties, but even then it's not that the originals/EE don't have them, it's just that they're not well implemented.
It is, except they could not use D&D, invented their own rules and those rules are a convoluted mess. I don't know what makes D&D rules special, but they are. I couldn't even finish the 2nd one in turn based mode and I absolutely prefer that one to active pause.
Actually the PoE ruleset is far easier to understand than 3.5e from NWN or Kingmaker. Not that I think that simple systems are good, as I do like complexity, but it definitely cannot be called a "mess".
If anything, the issue with PoE is its overreliance on "balance", an issue the second game suffers more from.
