I've noticed the same thing with my Kristofer Schanz character: It's really hard to build him up, and it's not even worth any bullets until he reaches around level 5 and has the "Firearms Training" skill. Currently he's being toyed with by a level 29 native warrior from Wiksick called MahaROGa, who cut him down to 3 HP and left him there until I used numerous First Aid Kits to get him back to 40 HP. The poison doesn't seem curable by First Aid Kits, though.