As the airline I fly for carries in terms of 40 million pax a year, medical problems like this happen quite frequently.
The co-ordinated response from the various departments that has been put in place works well - I have had occasion to use it twice recently.
On board medical kit and defib machine are well up to spec and constantly reviewed with the medical profession. BA indemnifies those doctors who come forward and offers in flight support through " Medlink" an Aeromedicine organisation based in PHX. In fact I fly with their number predialled up in the cockpit Satphone.
If all that fails we have no problem diverting - we even have special procedures for unplanned arrivals at non-gateway US airfields.
I wouldn't be too harsh on Airtours, at least they had something for the Doc to work with.