Wow, that sounds thoroughly miserable to me.
I've heard of such things, people marching off their demigods to wipe out pantheons, but always thought of it as a bore. If the GM is being that lenient with you and not bringing down the full weight of entire cultures and planets worshiping a deity, along with the deity's own firepower, then it's just masturbatory arena fight. And at that point I just see it as bad/boring GMing because no pantheon would tackle a group of deity killing demigods by their lonesome in some WWE match of one-man v. a dog pile of PCs. At that point might as well have the GM metaphorically fellate the players, blathering on how you win everything you ever do and are showered in glories and treasure wherever you go, forever and ever, amen. Tedious.
But then I find negotiating bill of lading contracts in D&D fun, because I see an actual challenge there... To each their own, I guess.