I'm going to go with "or what".

First time I ran into them, I gave it three tries - going NW from one of the train stations, to get north of Sloan. Group of three Deathclaws, me with Veronica. Around lv16, with a Cowboy Repeater as my best gun. ~50 sneak, ~60 guns.)
Every time, they just slaughtered us before we could get more than a couple shots off. Blazingly fast, saw through my Stealth before I could see them, took down Veronica in a couple hits, etc.
Total massacre.

(Note, I'm on a low-end graphics card, so my view distances are turned down. Makes sniping things a bit harder, when you see red dots on the compass at 6 PER, and can't see the actual guy yet.)