A heavily modified Gauss gun is like a rolled up newspaper, and the Deathclaw is a puppy dog. I was murdering lvl 50 - 52 Deathclaws, Legendary Deathclaws and Legendary Glowing Deathclaws at lvl 42 and in X power armor.
P.S. Sell their meat.. Nice caps.
P.P.S The three hardest enemies I have come across that put a Deathclaw of any type to shame, were a Legendary Sentrybot, A Legendary Glowing Mirelurk Queen, and a Legendary Putrid Bloodbug. The Mirelurk Queen was the most difficult, but I blame it mostly on my environment at that time. It was hard to get away from her. The bloodbug just wouldn't stay still, and the Sentrybot was just ruthlessly pursuing me.