If you like the feel of the Sojourn over the LHT and 520, then that is the steed that was made for you!
Disclaimer: I love disc brakes. They are, in so many ways, the perfect brake system for my do-everything bicycle. Now, with that out of the way...
Don't get disc brakes unless they are the right system for your needs. Disc brakes are for you if: you ride in the rain somewhat frequently; ever ride in snow and ice; don't want to do rim cleaning; or might want to experiment with different wheel sizes. If the aforementioned conditions don't apply, then you don't have to subject yourself to the weight penalty of disc brakes.
If you're still set on disc brakes, for the love of all that is brake-y, change your pads from the stock Avid pads to an aftermarket sintered pad. Right now, I am using Aztec and am very pleased with them. Previously, I used Gator sintered pads and was also very happy with them. Avid pads wear out too quickly, glaze too easily, and are overpriced to boot!