Actually, I was pondering the question, not just why there wasn't any smart Deathclaws, but had the Deathclaws always been in the DC Wasteland or did they come with the Enclave? If they did come with the Enclave, why are they so prevalent?
Deathclaws were a pre-war government experiment, there could have been some in the DC area as well back then. As for lack of intelligent deathclaws, all the FO2 ones are dead, and the experiment was a failure, so Enclave decided to try mind control instead.
Cats. Where else did they go?
See:
http://www.gamesas.com/bgsforums/index.php?showtopic=923883
The version I quoted in one of the previous posts is canon.