A little late chipping into this, sorry, busy, and on a bike ride on Trans Pennine Trail yesterday.
My Sherpa weighs 12.5 kg including rack, pedals, bottle fitments etc. It is a 530S frame, the smallest of the 'mid-range' frame series I think. This is less than a lot of other Sherpas, and less than other 'tourers' from other manufacturers. I guess the following things contribute to the low weight -
Wheels / tyres - DT Swiss rims, Deore hubs. These were . . . . not cheap . . . but have performed very well, lasted well and run 100% true after about 4 years on the Sherpa and it's predecessor, a Ripio. The rear rim is beginning to show signs of wear, and I must get it checked. 26 x 1.6 Supremes - roll well, and better grip on muddy trails than you would expect. Lightweight Schwalbe tubes.
Fork - the Rav 853 fork. A bit lighter than standard - good ride.
Tubus Vega rack
Transmission - XT cranks with external bearings, XT cassette.
I reckon the only way to reduce weight still more would be carbon seatpost, lighter saddle, etc etc. and I don't see much point in going that route - the gains would be tiny, as my present Thorn seatpost has not much 'spare' on it, so little surplus weight.
If I had bought all this at one go as a new Sherpa, it would have been a pretty expensive bike! But most of the components came from my Ripio onto a new Sherpa frame / fork, as I had tried to make the Ripio lighter - it was a lovely bike, but was clearly over the top in terms of weight and strength for my changing riding habits. So the bills were spread a bit.
I reckon in it's present setup, my Sherpa would cope with all but heavy touring, which would probably need wider wheels, stronger rack, and forks with low loader. But as a general day-ride, light - moderate touring bike, it suits me well.
The biggest change I made in terms of real and perceived speed / agility was in the wheels - rotational weight really does count, especially in my stop/start urban riding.
Lewis