Level of difficulty doesn’t match the difficulty?

So yesterday I was playing with a friends who recently got the game, so I’m raising the difficulty slowly while I’m playing with him. We deployed in Vog-Sojoth at level 6, the first mission was a bit more difficult than normal but I ignored it. Then comes the second one, we deployed and it was one of the worst I’ve ever played. The amount of bots appearing wasn’t normal at all. Specially the number of tanks, we encountered 2 every 5 seconds. I’ve played level 10 missions easier than this and it kind of ruins de game to my friend if as soon as he starst playing he gets thrown in the closer thing to Malevelon Creek since that hell ended.