A heavy bike feels very different from a light bike. But, pedaling up a hill, the total weight you are lifting (the bike, plus you, plus gear and water bottles, etc.) is where the difference is and if the difference between bikes is only 5 percent of the total weight, you are likely only 5 percent faster up a steep hill. In that case, a different bike might feel like it is justified, but would you be happy investing in the different bike for only a small improvement in speed?
Tires for an unladen or lightly loaded ride may be different than what you have on the bike, you might be able to make the Nomad feel more responsive and faster.
If part of a trip is lifting the bike up on a rack for vehicle transport, is the Nomad a weight that makes that difficult for you to do or not? I pick up my Nomad Mk II a bit differently than my lighter bikes because it is heavier, but I have figured out where to grasp it and how to lift it to make putting it on a rack less onerous.
I have a bike for every day of the week. Most of my riding is on lighter derailleur bikes. I use my Nomad Mk II for local rides that are mostly on gravel, I have 57mm wide mountain bike tires on it for use near home. But I still have several trips left in me and plan to use my Nomad Mk II for what it was built for in the future.
If you feel that a 700c Rohloff bike would make you that much happier, if you can afford it, then the decision is probably already made, you are just trying to justify it to yourself.
Four years ago, I did not need another bike, but I became aware of a new titanium frame on Ebay with factory warranty that so far had bidding at a small fraction of the new manufacturer price. I thought about it for a few days, I did not need it, but I had always wanted a titanium bike. It now is one of my favorite bikes and I am glad I bought it. If you really want something that will make you happier, that is something you have to decide yourself.