The best person to consult about this would be a fire engineer or even a fire investigator.
I believe that the way to approach the situation is to first of all considder the fire triangle (heat, fuel and oxygen) and put some figures on how much of each is available in various situations.
Since to put out the fire requires removal of one of the components of the triangle, it makes sense to have a procedure which seeks to remove that component that is easiest to remove.
Another point to be considdered is simply doing nothing with the fire other than landing the aircraft which brings up a whole different set of situations. The first question being, how long will it take for a fire to damage something that makes a safe outcome doubtful.
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As for doing nothing until at a safe height. This is often based on the principle that if the fire is the only problem, you don't want to shut down a working engine until you are at a safe height. If the engine no longer works then the priority is to avoid obstacles until at a safe height.
What defines a safe height when your ass is on fire is purely personal!!!
Regards,
DFC