A and D keys are not TURN left/right, they are Strafe left/right. Which means that your mouse is your directional control, just like the majority of games beyond the mid-90's that adopted FPS controls and camera mechanics. Holding the right mouse button is BLOCK because there's combat, but it will also lock the camera to the character direction. This is not a first person game, locking the camera to the character in a third person game is a bad deal.

So yes, this is a third person mouse look control with default FPS mechanics for WASD, and no, it can't be changed. At least not without some hardcore mods to do it. Best to get used to it so you can play other games optimally.
I used to change things like invert the mouse, put my wasd controls on the numpad and all kinds of things but it gets tedious doing that with games, and the ones that don't support that kind of thing were very difficult to play so I abandoned it and only tweak the things that don't conform to normal control schemes now. I hate 3rd person cameras that are configured incorrectly (low angle, too high angle, no zoom -too far, too close, bad position -not enough to see above the character, too much behind it, etc), but this game does it just right. I just hate it when games are like "hey I see you haven't moved the camera manually for a second, here, I'm going to put it to where I think default position is! hahahahaha".