I played and beat the game on hard difficulty, but not after finishing on the other two difficulties at least 10 times.
I learned a strategy that is very useful in beating Wheatley at the end.
Wheatley's fighting style is Muay Fly, and the two best fighting styles to use against Muay Fly are Ghetto Blaster, and Black Panther.
Oh and another thing: Wheatley's kicks look like they're going high, but are most likely going low, so block low, which is probably the advantage that Muay Fly gives you when using it.
Hopefully, this will help you become a BMF yourself, and be able to prove it.