Metrocop - 60 / 90 (extra health version for players with OP guns)
Soldier/Shotgunner - 90 / 120 (or 150)
Elite - 120 / 240 (or 150 / 300)
Based off semi-OP TFA assault rifles that deal 30-33 damage (at least that's what the stat says, I don't remember the default headshot multiplier for HL2/Gmod but I think it's 3, I wish I knew how to increase NPC weapon damage since I personally spawn myself with double HP and armor)

I think this would pair well with MMOD combine (if there's an addon for that)