Just saying - current diablo3 AND this new version are both the same "point of view": an external camera looking at the character.
1st person: me, mine
2nd person: you, your
3rd person: them, their
Now you could make an argument that it is 2nd person, if you are considering the avatar on the screen to be "you."
But traditionally... you are not your character, so they're both 3rd person.
So given that they're both the same "external camera looking at the avatar," the question should be
what if it was an over the shoulder camera (3rd person) instead of fixed isometric (also 3rd person). The over the shoulder camera, once that's enabled, also allows 1st person view by zooming in until your screen = your character's eyes.
The real question is why is it a FIXED isometric view? Why can't you simply change the camera around? Does that detract from some of the engineering of the assets? Does the "zoom in" feature imply that the world is entirely 3D?
The biggest problem you can already see with the mockups is you get almost zero vision behind you, for an increased forward vision that doesn't help much with decisionmaking. This reduces the speed of the game tremendously, when you actually have to go up to a corner to see what's behind it. There's absolutely no way that some of the speed builds would work.