play as "noble" with rapid-bow with leech mod
1. hire a ranger for big gun and his ranger buff (give him gravity gun or rocket launch)
2. hire militia for big gun and da bomb (grav gun or rocket launch) -- the random nades are awesome too
3. hire guardian, pump up his shotgun, give him auto-shotgun with skills in disarm, defender and leadership.
this is the best combination because rapid-bow & leech with noble's increased damage & accuracy will clear a lane very fast, and combined with a good grav gun you can keep the field clear mostly of the time. rocket launcher is a standard and required to destroy armor and those at the wall. and shotgun with disarm can keep the damage to a minimum. remember to max out leadership and defender - these will really help defense and your AI.
i'm on day 87 and i've use henchman about 10 times.