I now know why some players are reporting barbs being more difficult. I just had a game where the same barb camp (on the same exact tile) respawned x3 times directly after I moved away and lost direct sight of the tile. At one point, I had x5 barbs scouts around my starting city.... waiting. On disaster rating 3 or lower I never had this issue, but only had it on disaster lvl 4. I'm not sure if there is a hook for increased barb difficulty there but it felt like it.