The snarlnuke only works once if someone calls his bluff. TDO can keep asking for whatever he wants forever as long as the other gods think it's better than being annihilated. As long as the new world order gives the other gods enough worship to stay alive, they'd go along with it.

Agree that Xykon controlling the Snarl would probably be worse. When he claimed he wasn't out to destroy the world, he admitted he might do it if he got really bored. Unlike TDO he might not even wait for someone to call his bluff before using it.