Racer Ex 

My answer is I don't do long low cadence efforts, at most I'll do 2 minutes (or to failure) at a very high wattage and torque. Being a part time track guy I'm using low cadence strictly to develop peak and short duration power, and not in any aerobic capacity. If anything I'm trying to push my cadence up for track racing, and I've got fragile knees which aren't happy grinding in any case.

It's been my experience that some people can benefit by going to a higher cadence than what would be self selected during training...moving that selection point upward over time and getting the benefit of the reduced force peaks discussed here. Riding like the OP actually goes the other direction.

I watch a lot of people climb and 90% of the time I can tell by cadence and pedal stroke who will be there at the end of the race. Slow mashers usually don't make the cut. One of the biggest outliers to this was watching an track Olympian who pedaled away from most of us at an annoyingly slow cadence on the climbs at Gila. Completely opposite of what you would expect.

I don't generally see a positive training response to long, low cadence climbing and the benefits that I have seen could be accomplished faster by other means. But that's not to say some people may not respond to this type of workout differently.