People really don't know how to use NPC's in F2...
Rule nº 1: give them cheap and weak weaponry, but good armor, while they're low level. Just being there helps a tiny bit in the early game.
Rule nº 2: avoid combats you wouldn't win alone anyway, like Raiders between Vault City and NCR - at least until you have everyone, including yourself, using Metal Armors and at least 14mm pistols. The only real dangerous battle from this point until the San Fran/Navarro area is the on against Darion at Vault 15 level 3: those 2 guys in Combat armor, wielding Assault Rifles, are a pain. Also, Darion's flamethrower is nasty.
Rule nº 3: never give them burst weapons before everyone has Power Armor (preferably, never give them at all). Exception to Cassidy, who can be told to 'be absolutely sure that won't hit' you - but then again he will rarelly burst, and these weapons are weak in single shot mode...
Rule n 3: level them up as frequently as possible - save, level up, load, rinse'n repeat until they level. This is better done when leveling up by quests, which by the way are the moments were level ups occur most frequently, at least until around level 15. Fact: high level Sulik, Vic and Cassidy using Gauss Rifles kick all kinds of ass. Blowing ribs is Cassidy's favored sport
Rule nº4: NPC's don't get addicted nor suffer withdraws, so drug them! 2 doses of Jet = 2 AP, Psycho = 30 Damage Resist, Buffout = 3 Endurance (better HP and Damage Resist as well).
I just cleaned Navarro this afternoon, and I came through the front door!
Hyjal (me) = Pulse Rifle & APA
Sulik = Gauss Rifle & PA, close to me
Vic = Turbo Plasma & HPA, close to me
Cassidy = Gauss Rifle & HPA, sniping
Marcus = Turbo Plasma, sniping
Skynet = Gauss Rifle, sniping
No casualties. Minimal wounds, low stimpack usage. All loot taken to San Fran in one trip.