I've tried night fighting with NVG vII on my mercs, it rarely seems to make a difference. This is probably just a PEBKAC issue. By the time the enemy is within my field of vision, they're close enough to pop everyone's heads open with those adowable little pistols. I've tried both long/short range weapons in these situations, and unless I hide around the corners of buildings the whole time, I just get swamped with 4-5 guys who I can't kill off in a single round... and then it's their turn. We get AP drained into a cycle of immobile death. I reload from my last save.
Regarding my mercs, I couldn't afford anyone better in the beginning. I actually had to restart the whole game once already, because I noticed my expensive merc (I think it was Lynx?) was getting ready to leave and my income from Chitzena still didn't cover a single week of re-hiring them. Email informed me that Blood died on assignment elsewhere, so hiring him was never an option.
After restarting (ironically, this is when I bumped up the difficulty level for some reason) I took Barry for his wis/mech and took the advice of a forum post, that basically said to go through San Mona first (because no enemies), do the quests there for a bit of money (I think it ended up being around 30k) and then take Chitzena. Then I holed up there, training militia until they were numerous/experienced enough to ward off attacks without my mercs. Then I went and took out N/S Drassen and did the same thing, leaving the central tile to last.
I think, with two mines, I'm finally ready to hire a decent Merc and keep them around. But damn that took a long time and a lot of very long, very savescummy fights. Enemies would attack in frequent waves of 10-20 and call reinforcements from adjacent sectors, meaning fights would often involve 30 or more enemies against IMP, Ira, and Barry. Eesh... It's even worse when I get militia involved. I auto-resolve as many fights as I can, but those victories don't drop equipment. The bigger battles
look impressive, but NPC turns tend to drag on a very long time (I watch QI in between my turns). The plus side to this is that militia seem to have the same NPC Pistol Magic that the enemy does, having uncanny accuracy and the ability to headshot at mind-boggling distances.
Having said all that, it's still a very small frustration when compared to how much enjoyment the rest of the game delivers. And the reward of picking through pages of loot after a successful defense sure is worth all that hassle! Getting everyone properly equipped doesn't seem to make much difference to
my success, but it's nice to play dress-up and pretend we're all badass killers, even if we suck.