I also find that having 3 or more specialist hires is seriously a really great deterrent.
Mainly because nobody even knows what the 3rd is going to be.
In my round 1 Topkilla Tournament game I was turtling at this one outpost, which was about to get taken from a 200+ driller sub, but I had a double agent in the 3rd hire which saved my life! Without it I wouldn't have progressed to the 2nd round lol