Played for 11 hours now. Still only done 4 main missions. Been focusing on grinding out the red missions for power. Not sure how many captains you can kill off before they repopulate, but had it down to a total of 5 left (including ratbag) when I died and 5-6 more added.
Unlocked tier 3 power, and one of the 2500 abilities. Aside from the swarms, I rarely have problems with the captains now, which is probably due to me not progressing the story. Not sure I've seen any vendetta missions, only ever killed my nemesis orcs.