I found shotguns to be very useful against cultists early on. Take a cyborg out and have him wave and make crude gestures until you get a cultist's attention. (Your mother stinks of elderberries!) Then have the cyborg run back through a door so there is a wall between you and the cultists. The cultist will give chase and as soon as he comes through the door you can feed him two rounds of buckshot. Rinse and repeat until there are so many corpses piled there you have trouble aiming through all the "dead" tags. Then move to a new room and rinse and repeat!
It helps a lot if you have a guy with a second level of leader already. That gives you the damage you need to take out those big brown, stocky dudes with the big guns.
I cleared a cultist base early on with just a cyborg using his shotgun. I had other guys along, but didn't use them much. The cultists stayed in buildings until I got just outside the door. So they all ran out the door single file to be slaughtered by shotgun shells. It was kinda sick actually.