Airclues,
On your mention of a decision to divert.... services such as Medlink, using qualified doctors, will advise for or against a diversion given the facts known at the time and available to them. In certain cases I believe they can pronounce death in which case they would probably advise continuing to a company port so that the affected crew can be stood down and supported by their colleagues and company personnel.
Of course, the captain/PIC always has the last decision but Medlink will give any and all necessary advice. They have legal liability to make decision on behalf of the cabin crew and cabin crew if following directions of Medlink are absolved of liability, given they follow said instructions to the letter.
Hope this helps clear it up a bit.