Would do the complete opposite? Make exporation and combat more of a pain in the butt?
Frankly, if you go for the top down perspective, the game should be playable without flipping the entire world upside down all the time. I got Dvinity: Dragon Commander for free a while ago and booted it up recently. Wow, the camera might make me not boot it up ever again.
I agree, it should be playable without doing that, but I often found myself wishing that I could rotate the camera during combat in PoE I. Don't see how rotating would make for worse exploration though. At worst you can always ignore the feature. The only thing it would do is make things much more expensive if you want to achieve similar visuals. Games like Exanima show how this can be done.