I think the comparisons with Audley Harrison seem to be very harsh, because he truly was fighting bums time and again, whilst Khan has been stepping up the opposition and building up the quality he's facing.

1 former world champion
1 former world title challenger
1 Commonwealth champion
1 former European title challenger
1 former British title challenger

and those are his last five fights. Combined record of 131-12-6.

Audley Harrison's five fights at the same stage of his "career":
1 Polish Champion
1 former British Champion (who had lost the 6 fights before that one)
1 WBF "world" champion
1 guy with 3 losses in four fights previously to the fight with Audley
1 guy with a 7-4 record.

Combined records of those 5 : 95-31-2.

Stats can explain almost anything when spun correctly, but these tell me that Khan is a different league to Audley at the same stages of their careers.