Well, you don't have to be intelligent...
If you could be a deathclaw, you could overclock your strength to new hieghts, and your intelligence would be 1 or 2. Plus, the possible endings for FO1 don't exactly fit in w/ the story for FO2. Like if you don't rescue Tandi from the Raiders, or if she dies while rescuing her, the narrator says, "Aradesh grieves over her slain daughter Tandi." Plus, if Shady Sands gets raided by mutants in the end, what happens to her? And there she is in FO2. So even if the intelligent deathclaws are dead (except Goris), there are strange possibilities that you can be a smart deathclaw.