Don't be so sure that the derailleur has suffered no damage. Once you have it remounted on the hanger get the bike drive train up near eye level, with derailleur in the small cog and middle/small chainwheel (triple/double) and sight toward the front. The pulleys should be in a vertical plane and should remain in the same plane as you pull back on the derailleur and therefore rotate the pulleys. If not you have some twisting of the derailleur and it will not work optimally.