The thing that really impress me with the XPS's is that they have that lovely neat form factor and yet still allow user replaceable RAM, SSD, batteries!
So without meaning to patronise - your problem is not the weight of the bag its the shoulder strap. Any bag that asymmetrically distributed across your shoulders will hurt after long enough. A backpack is a much better solution ergonomically. What I do when I'm travelling is use a backpack, and simply shift it around on my shoulders so that it is to my front when I want to access something. It takes a little practice but now I often do this while carrying another bag also. Now I'm usually not doing this to type on a laptop however, but its easier for accessing the bag than unloading everything from my back!
There is also some special use options: https://www.wolffepack.com/pages/learn-more#
Just found this googling I've no clue how good it might be
another make: https://www.mindshiftgear.com/products/rotation180-trail
again no clue how good it is - Edit: might not fit a laptop:
Thanks for the tips - I'll give a backpack a try I think. Though there's still a little envy when looking at the XPS at half the price for a similar configuration, a bigger battery and a smaller, thinner and lighter enclosure.