For the purposes of Argent Adept and Akash'bhuta being each other's nemesis, are her Primeval Limbs considered to be her? For example, Living Rockslide says "this card deals" damage. Is it increased against Argent Adept? If Argent Adept hits a limb, is it increased?
Not as far as I know. The only card that Akash'bhuta has that does damage directly is Entomb. Mind you, it's not as if the Argent Adept has massive numbers of damaging abilities.
It is only a nemesis if it has the symbol on the actual card, like Anubis. So yeah, AA and AB being nemeses is almost irrelevant.