Wow... must say I learned a lot from this thread!
I still think, and correct me if I am wrong, that fatty tires are the only reliable option for "full" suspension (albeit without the damper) when you tour with a heavy loaded bike - both front panniers and rear. Full suspension bikes just can't handle it.
The price to pay is higher rolling resistance.
I also understand that if you want to minimize those rubber losses on the fat-tires, you must inflate them to "rock hard" pressures such as 20PSI, where they would be more stiff and create more vibrations and shocks than 2inch tires at anything below 80PSI. (80/20 = 4 = 2^2 according to the diamater difference)
Still I think, that for long-distance touring in countries with really bad roads and surprisingly deep potholes which can ruin your trip if you would have a typical 1.75inch tire at 80PSI, the Fat-tire at 10PSI will save your bike, your trip, and maybe your life.

For such benefits, and the ability to lower the pressure even further for accessing off-roads, I think I am ready to pay that extra rolling power-loss. (especially since this is an E-bike tour)
This is where the Surly Blackfloyds (26x 3 . 8inch) fit perfectly, although Surly originally designed them for "When Fat-Bikes want to run". (Which is kinda silly considering the much higher rolling resistance).
There is one more question which came up now - Is there a higher wear and tear when you run a fat-tire at 10PSI vs 20? This could be significant on a long touring journey. I tend to believe, that as long you don't go crazy low on the pressure so the tire is almost coming out of the rim at curves, it is exactly like obeying the minimum pressure limits of "Standard" 2 inch tires.
Am I correct?
And if there is much more wear and tear on the lower allowable pressure limits, is the ratio of wearing can be compared to a 2inch tire? For example, if running 2inch tire at it's lowest allowed 40PSI (for the sake of the example) makes the tire's life shorter by a factor of half vs at 80PSI, I can assume the same ratio for the 4 inch tire when you compare 10PSI vs 20PSI?