Deathclaws ("DCs")

A lot of people on the Web claim that they can kill them with a few shots from an Anti-Material rifle or even lesser weapons. 
I recently went in equipped with an A-M rifle, a grenade launcher with a long barrel, a 12.7mm SMG, a sniper rifle, and a missile launcher with a guidance system, and more. I had all the different kinds of ammo for each. I was level 26 and had 100% condition Guns and Explosives and all the fighting drugs and magazines. 
It was not uncommon to have 2 or 3 Deathclaws spring out of nowhere and kill me instantly. Anyone who claims that they can kill all the Deathclaws easily and/or quickly are playing a different game than I am.  

Weapons:

Missile Launcher - when the DCs are far enough away. 

High-explosive missiles are best for more than one DC 
Plain missiles are okay if there is just one DC, but it may take more than one missile. 
High-speed missiles if DC(s) move around a lot.

Anti-Material rifle - for medium distance. A grenade launcher can also be good. 

With either one, I use the fire rounds.

SMG - The 12.7mm if available; otherwise, a 10mm. For emergency close-up work 

No kind of SMG is going to hold off an un-injured DC, but you should survive an injured DC.  
I never shoot one of the above weapons at a DC who isn't a long, long way off and with me up high somewhere. 
If one pops out of nowhere or comes charging in my direction from far away and is getting so close I have to use an SMG, I read a Milsurp (Guns) magazine and pop some fighting meds.

Location:

Deathclaws are in and around an abandoned quarry with some large equipment in it.
The east side of the quarry is open to the road running north by it from Sloan.
The other sides of the quarry are blocked out by mountains which makes it more difficult to get through to the quarry, but there are more DCs in the hills around the quarry than there are in the quarry itself. So even if you can work your way across the hills, you will often find yourself surrounded by DCs.

Where to Attack From:

The easiest way to get into the quarry is going up the road heading north from Sloan which itself is below the southeast corner of the quarry.

Continuing up the road, there is a hill running along the north side of the quarry. There are 5 or 6 Deathclaws on the north side of the hill. If you see their red pips about a 4th or 3rd of the way back, you can go up the hill where it starts near the road and walk towards the back until you see a couple of them.

From up in the hills and a long way back, it should be safe to fire at them, but they run around when you do, looking for a way to get to you. Run back towards the road and to Sloan, if necessary. Boone and ED-E will stay closer to fight them and you can snipe them from a distance.

Actually, the safest way to kill the DCs on the north side of that hill is from the hills further north.
Even with a Perception of 8, I was getting no red pips from the DCs described above. When I zoomed in with my sniper rifle's scope their outlines provided by the beret given me by Boone gradually appeared and I could see 5 or so DCs moving around close to each other.  
I thought the best chance of getting them was with a high-explosive missile, but they did not show up in the launcher's scope. I fired a missle blindly at the spot and it looked like it was going straight at them, but it never exploded. I took that to mean they were out of the launcher's range.  
So I went back to the sniper rifle. When I hit one, it did not show a red health bar. Instead, it flashed a red heart to the left. After I hit one 4 or 5 times, it would fall over dead. I kept this up until I finished off the north-hill gang of DCs. 
The scope mod for a laser rifle is said to be the best in the game and with the other mods for it, I think it would have killed the DCs more quickly, but I normally don't use energy weapons.

Once I have killed the North Hill Gang of DCs, I fast travel to Sloan and walk back up the road to the quarry. A DC is usually on this side of that big machine seen below:

After sniping it, walk around the boulders on the left, climb up on them and walk until you see the way it looks in the first picture below. Zoom in to see two DCs and start sniping them. Using fire rounds makes it easier to see your hits. The advantage of shooting from this distance is that they can't figure out where you are, so they will stay in the same spot while you snipe them.
 

Once you take out these DCs, continue walking the way you were going until you see some red pips in the far western part of the quarry. They will be on the ground level of the quarry. At times they will duck behind cover, but be patient and they will expose themselves again. The most important thing is to keep your distance.

Keep up this approach until there are no more DCs.

You can walk to the Kahn's encampment fairly easily after clearing the DCs out of the quarry. It's just a long walk and a little complicated. It's near the top of the west end of the quarry.

A shorter and easier walk (again, assuming the DCs are gone), is from the north. See this page.

To get credit for clearing out the DCs, you have to kill the Alpha Male and the Mother. then you can turn in your accomplishment to the Champs Lewis just outside Sloan.

Last time, the Mother and kids were nestled into one spot and I just hit them with a few missiles. This time it was a lot harder and the Mother was chasing me all over.