My thought is that merchant vessels in Vargr space are well armed with crews ready to counter-board if attacked.
This is like the age of piracy in the Caribbean. Trade didn't stop. The Spanish sailed galleon's full of gold right through the middle of the pirates. But every mechantman had to be ready to defend against attack.
It would seem to me that the way to protect against pirates in 400-dTon Rrazaghz Class Corsairs is to use larger merchant ships, say 5000-dTons, with very long ranged 50-dTon Particle Beam bays able to kill pirates before they get close. The best merchant ship captains would be former pirates with a nose for ambushes and a willingness to shoot first. In this scenario, merchants have the advantage. They would be willing to destroy their enemy as long as they got away safely. Pirates need to close with and capture their prey. Destroying the merchant ship leaves them without any loot.
If you look at the modern day Straits of Bab-al-Mandab, a piracy hot-spot, off the coasts of Yemen, Djibouti, Ethiopia and Somalia, large oil tankers, container ships, and general cargo ships transit there everyday. Yes, some get hijacked, but nations have set up patrols to deter pirates, and the shipping companies have put mercenaries on-board to drive off boarding parties. Merchant ships taken by pirates are more often held for ransom. The pirates don't generally have the means to resell the ships or their contents in any meaningful way.
To me, the Vargr Extents would be Dodge City, everyone armed to the teeth, tip-towing around everyone else who is equally well armed. Yes, your cost of operations would be higher, but so would everyone else's, so the extra cost would just be baked into the cost of doing business.
- Kerry