"In fact, if somehow you know for a fact that your opponent has a middle or small pocket pair, and the flop comes A, 7, 8, 8-8 and 7-7 are actually the least likely hands for your opponent to have."

Yes, but if you have say AK and raised 4x BB preflop, and get just a caller, they probably have you on high cards. If you bet hard after the flop, and they jam a reraise on you, or if they bet out really hard before you, i'd say its most likely to put them on that set or that 87s.