is it supposed to be like that?
The thing works by relfecting the light emitted by the red LED back towards your eye. Since the LED is on the side of the tube, the lens needs to be at an angle to relfect it.
Neat picture from aimpoints website:
As you can see, its 2 lenses not just one, but its angled so the reflection of the LED is always parralel to the optical axis.