Kudos to Audio Research

Jab-I think I would have to disagree with you on that point
as a bad tube can bring down a amp if the design is not there to protect other components that maybe involved;if a tube shorts biasing resistors and/or caps may burn as well as tube sockets;level of damage can be a simple resistor to as melted area on the circuit board or tube socket.

Friend of mine who has a Audio Research amp sent it in to be fixed.
His amp is from the early 80s. It cost too much to get fixed so he asked them to please send it back.
Much to his surprise when his amp returned from ARC all of the parts that needed to be replaced were send along free of charge.
Good on them.

Audio Research guarrantees their tubes for a time period so if they take out an amp, they should repair it, and obviously do.
Regarding a tube taking out the resistors and some circuit traces, Audio Research feels, I think, that there are compromises inherent in designs which protect the amp in the event of tube failure. It would obviously be easier on them the design amps that way, fewer repairs, but they are a perfectionist company and strive to have no shortcuts to sound quality. I am not saying that other companies are taking shortcuts, just a different approach.