I can see a way around in a way: if the claws hit the character for damage, then poison applies, because in most cases that would mean that through clawing or whatever means the poison has entered the blood stream. Although that still leaves quite a few open endings.
I've experimented with stacking Venom and Claw damage in a game, and it is overkill. The Venomous ability is doing enough damage that one can take for granted that some of it is "Claw" damage.
Also, I fear that folks may be forgetting that this system is an abstracted narrative mechanism, and not a point-based, finely tuned combat simulator.
I also support Toughness as providing sufficient defense against the physical stress of a Venomous attack (unless Poison/Venom is the Catch, of course), since Toughness powers are a combination of several effects rolled up into one, the sum of which covers the Armored Skin portion as well as the general increase in the heartiness of a creature with the ability.