Shouldn't a behemoth do more damage than a (at least a normal) deathclaw? It's, like, maybe two times (or more) a deathclaw's size and armed with a fire hydrant mace. A fire-hydrant-mace. :O
The fallout wikia nv has a deathclaw at 125 dmg and an alpha male at 300. I know the deathclaw hand is magical and mystical, but....a fire hydrant mace...
Or maybe you could give the fire hydrant mace armor piercing capabilities? That would be historically accurate, from a mace point of view. Maces were very effective against all forms of armor because the force penetrated. Blows like that would cave in plate armor, pass right through chainmail (or equivalents), and deal much more damage to armor-wearing opponents than a bladed weapon would (like a deathclaw's claw). When swords were used against armored opponents, the gaps in the armor were sought out because the armor itself (even chain, with a gambeson/padding) was good at stopping the blow, especially plate-based armors. Swords were often used in two-hands with a hand reinforcing the point, and used like a short stabbing spear because they were so ineffective against plate.
So, if the Behemoth could have armor piercing capabilities, that might balance its attack out, imo. Is that possible? Too much of a change?