Personally, things like this have to be adjusted for a proper hang and to be even.
I really like just screwing a good screw into both sides of the mirror equally down and equally in. Then run a semi tight wire from each screw and secure it with 5 or so loops around the wire and tie it off.
Now you have a wire that is below the top of the mirror and slack enough for adjustments here and there.
Its done, those saw tooth mirror hangers only give you several adjustments and that might not be enough. And sometimes you cannot mount them because there is not any wood where they must be fastened.