Concours, this thread scares me too.
The checklist is excellent. Just do it, and you will survive. The checklist will descend the aircraft. Which is what you want. Who wants to stay in coffin corner with unreliable airspeed? Not I, and not Boeing, that's for sure.
Ignoring a checklist in this circumstance could only ever be acceptable if following the checklist would further jeopardise safety. About the only example I could think of would be traffic below. If traffic below, simply turn off the airway and then follow the checklist.
If you were the F/O, and had an unreliable airspeed in the cruise, and the Captain said "I'm just going to set 2.5 degrees and 85%", what would you do?
Personally I would say, "No, there's a checklist for this", and "Maybe 2.5 degrees and 85% is correct, but will doing that improve safety? No? So let's follow the checklist.". If that didn't work it would be "Taking Over", and set the attitude and thrust from the QRH memory items.
Once the memory items are complete, we can reference the remainder of the checklist, and have a discussion about whether the Captain would like to resume being a Captain.
You see, when you start to vary SOP's, it can only be for a significant improvement in safety, and there are 2 pilots on that flight deck. They both need to be in the loop.
In both Air France and Air Asia, one pilot was doing the wrong thing, the other pilot knew it, but failed to take over properly.