Many people carry heavy barrel rifles for predator and varmint rifles. At least the rifles that are named "Varmint Special," "The Varmint Destructor," and such like usually feature heavy barrels. I would guess that the hunting for varmints and predators typically doesn't involve long hikes and does involve a lot of sitting still in one place, and a heavy barrel in this circumstance shouldn't be a big deal.

I have two rifles that my father built in the late 60's early 70's based on Springfield military actions: one is a .30-06 and the other is a .25-06. Both weigh about 11 LBS. I just carry the rifles. I love them. They look really great -- nice walnut stocks, but substantial stocks not toothpick-thin stocks, and hence heavy. I'm 6' 2" tall and try to be in good physical shape when I hunt. I figure if the average hunter is 5' 10" and prefers a 7.5 LBS rifle, I ought to be able to handle the heavier rifle with no problems. If you are concerned, just do a little extra arm conditioning with dumb bell weights.