Welcome back! If you have four Njerp camps around you, you are probably close to the Njerp cultural area? Sami modified things a few versions back to make Njerps far less common in the west of the map, but of course that means you find more of them in the east.
I agree foreign traders should be a rare encounter. Personally I would like to see them confined to the Driik lands, or even better only in a couple of trading posts on the south-west coast. It makes no sense that they would go wandering into the wilderness for a week or two on the off-chance of meeting a trapper with some spare furs. Part of the trapping/hunting lifestyle should be loading up your furs every so often and taking them to civilisation to sell them.
I usually set up in the east, as far from any villages as I can get, and yes my hunting grounds are heaving with foreign traders - but bear in mind that foreign traders are probably the most visible creatures on the map by far, being a group of half a dozen men who unlike animals want to be seen. We see more of them, but they are likely not the most numerous living things around!
If the traders can't be in trading posts or around the Driik areas, I would like to see them stop moving. If I was in a wilderness and wanted to find trappers to trade with, I would set up a camp and keep a large fire burning. Far more likely that the trappers will see the smoke and come to see who is making it, than finding them while stumbling around the forests blindly. Seeing smoke on the overland map would be a great addition in general, as it would have been the usual most visible sign of human habitation.
I have moaned about this loads of times, so your questions are more suggestions than bugs