wizards are capable of getting injured...note....Harry breaks his arm in book 2, and what about the injury to his leg in book 4, and i beleive the irish seeker breaks his nose during the world cup too....
they just heal faster because of potions and magic spells and stuff.....and theres ways to slow them down when they fall from a great hieght....for instance neville bounced and Dumbledore slowed Harry down when he fell in book 3