I'd personally take the chance, but as above posters said, would come armed with a print of the rules off Timatic, also printout of your onward itinerary and ticket # on a different PNR, and arrive at the airport an extra hour earlier in case the point needs to be argued. As you won't be the initial guinea-pig for Air Asia, chances are decent it will be working smoothly and the agents will know about 72 hours' visa-free transit in Shanghai.
Chinese Immigration in Shanghai will not be a problem, that is for certain.