ZDHart

Some non-race hardtails are spec’d with 2.6 tires …helps smooth out the ride to account for lack of rear suspension. you also have a ALU frame. Race oriented HTs often have 2.3/2.2 tires. I ride on pavement with those sizes without issue.

Also, your Rosco 7 has a much slacker headtube angle which will feel slow compared to your Trek Dual Sport - your observation of a lack of nimbleness could also be due to the 65deg HTA of the Rosco because you state you mostly ride the of the DualSport with a 71deg HTA. 65 is more slack and appropriate for steep downhills on trails for confidence of not feeling you would go over the bars. In general, road/gravel bikes have HTAs between 71 and 74deg, as a comparison.

Having a second wheelset will set you back $$$ a bit….along with wheels, tires, you have to buy two new rotors and a cassette. if you are not riding it 50% then it seems a waste.

I think you just need different tires on your current 29” rims. The XR4 tire are not aggressive, in the wide world of MTB tires, as Veganbikes mentioned.

Check out the bikes you see at the trailhead when you ride the Rosco. Even ask other riders about how they like their tire set up. obviously ask your LBS who know the trails to recommend a tire replacement. This BF online crowd is from all over the world, and we all ride differently.