I'm around NCR and I currently have Vic kitted out with a Combat Shotgun and Metal Armor. That's some expensive gear. He's got nothing to complain about!
But half the time when a fight starts, Vic legs it in the other direction on his first turn before he's taken any damage and without firing a shot. What a Pussy! I forget the exact Custom Combat Controls that I'm using, but even when I tell him to "snipe the enemy", he runs.
Cassidy's got a freakin' heart condition and he runs around pumping bursts from his combat shotgun like he's afraid I'm gonna charge him for the shells he doesn't use.
Sulik is the master of shredding people with the point-blank SMG Burst - the SMG is practically a melee weapon with him. Fine by me, it cuts down on the friendly fire hits.
I'm starting to wish that I had never upgraded Vic from the Scoped Hunting Rifle. I don't feel like scrounging around for a Sniper Rifle at the moment.
The only time I got him to put up a decent fight was in the Raider Barracks Cave. I locked the fucking gate on the chicken-shit, so he couldn't run away! He still stayed right near the locked tunnel exit and hardly shooting while the rest of the party moved into the room. At one point, a Raider who was out of ammo for his gun ran up and started smacking Vic around in hand-to-hand, so Vic had no choice but to defend himself. Then Vic strarted running across the room, probably trying to reach the lader to the manhole exit. But when too many Raiders blocked his way, he finally started shooting again.
I'd shoot him in the Nuts for Cowardice if I hadn't taken the Fash Shot Trait! ;-)
Anyone know how to make Vic stick around and fight?

Does he have a crippled limb? That will almost always cause a character to bolt from combat.

Hmm...
I'm not sure. I don't think so, unless he starts out crippled when you recruit him. I remember he ran away from the very first fight in the Den (gang war at church), practically before anyone on my team was even targeted.
I have the Awareness Perk, so wouldn't the gimp limb show up when I checked on his hit points? I think he's down maybe 2 left over from a previous fight.
I guess I'll make sure to keep him healed all the way up before any fights start. I'll also try taking him to a doctor at some point and see if that helps. I could also try to fix him myself, I have a Doctor's Bag in the Trunk, and I've been buying up the skill so I can take the Living Anatomy Perk.

Keep using "doctor" Skill on him until you get a success, it would repair his hurt limb if he has one.
I'm not sure if a stimpack fixes that. If his arm is broken he would run since he can't use a weapon.

Vic is practically useless, should be obvious from talking to him and the guy you bought him from. Though you can always take him to Vault City, there's someone there that might want him. Can't remember if you get anything though.
And you really should give Sulik a melee weapon, which he is best with.

Do you mean his daughter? We already talked to her. I found her some tools, and then she gave me some better tools, which I traded for parts to get the car running.
Can a Melee weapon really do as much damage as a Burst weapon at point-blank range?

Yeah I'm pretty sure you could more or less give him to her. Anyway, as far as I know he is rather useless and a waste of time and whatever else you use on him. Should rather get Marcus and give him an energy weapon. Vic is just cannon fodder.
Can it? Probably depends on the melee weapon, but that is not the point. Sulik is skilled with melee weapons, pretty sure a super sledge in his hands is much more effective and less lethal to people you don't want to hit. Plus a melee weapon won't run out of ammo... Well most of them anyway..
Marcus is really the only one I ever bother to pick up, only one really likely to make a difference later on.

I ended up taking his combat shotgun away and giving him back a Scoped Hunting Rifle. Then I killed some Raider who had a Sniper Rifle and gave that to Vic. He still tends to run around a bit when combat starts. For distance, I have him set to "Snipe the enemy". Maybe he's trying to run away to "sniper distance" and "medium" will work better.

Vic seems to be working correctly for me, I have the restoration mod installed and thats it.
However, Vic is turning out to be the biggest let-down in npc's so far. Sulik has the Super Sledge, Cassidy has a guass Rifle and other rifles. They perform great. Vic never seems to do much damage and/or takes the most damage. Sulik is in power armor, Vic metal armor and Cassidy combat leather armor. I'm in advanced power armor.
So in the ending, with my car, I tote them around when I travel. Then tell them all to sit by the car when I get where-ever.
NPC's seem like much more of a hassle than a benefit atm. Clicking the Push-away button all the time! So I have them there and ready (and holding vast quantities of stuff =)), until needed.
Disclaimer ~ Going solo most of the time is challenging fun!

I took away the shotgun and gave him a sniper rifle.
Adjusting the distances seemed to help a lot. I think the combination I had was "snipe the enemy" and "keep your distance" or something like that. It was causing him to use up all his APs trying to get far enough away to qualify as "sniping". After I made the changes, he was more likely to stand in place and start shooting once combat started.