Just now I had to give up on a mission because of a Rookie OT Huntsman that was listed as 1 level higher than me.
Reason, it was hitting for 22 each time and was getting 2x as many hits as I was in the same amount of time! Plus its damage shield never seemed to wear off even after 15 mins of solid combat and it didn't even rebuff once. And my Mausser, which usually hits for around 36 was hitting for an average of 12! Maybe there was some mistake with the MOB's AC level, because the only visible armor it had was a flak armor vest.
I've had to give up on about half the missions I've taken because of this problem (usually after spending about 20 mins getting there...) and it REALLY annoys me! >(