In F3 deathcaws bothered me very early in the game. After I reached level 12 or 15, they were easy unless one somehow snuck up on you.
The ONLY way I could see them being a problem in Vegas, is if one spawns right on top of you....and I've seen enemies spawn right on top of me several times.
I can see deathclaws far enough away that I've yet to have one get close enough to hit me. I drop them from several hundred yards, usually one or two shots of .308.