There are several ways you can combat Deathclaws and live to tell the tale.
1) Get a shitload of mines. Frag mines work best, but plasma mines work too. Get about five to eight of them and place them in one big pile. Get the Deatclaw directly inbetween you and the mines and get their attention. Make sure you stand back.
2) Anti-Material Rifle or This Machine with armour-piercing rounds. This is the expensive route, but also the easiest.
3) Mini-nukes.
If you're low level and poor, there are two ways you can deal with them.
4a) Find a rock and place yourself on top of it. Make sure there's no way the Deathclaws can get up onto the rock, otherwise you're screwed. The Deathclaws should pile around the rock trying to swipe at you, regardless of the fact that they can't reach you. Have fun.
4b) If there are no rocks around, make sure you have a decent mid-distance weapon. Something like the laser rifle will do. Aim for one leg and keep shooting at it until it's crippled. The Deathclaw should now walk pretty darn slowly toward you, allowing you to just walk backwards and shoot at it until it's dead. For maximum safety, cripple both legs.
OR.
Get Boone. Problem solved.