The random scales is intentional. The AI is supposed to play a pretending god with an effect on his lands. It is not supposed to be a god trying to maximize the outcome of his subjects lands. So should you if you play SP
I'm not sure, but thought that SP players were less concerned with beating their opponent and more into role-playing. If you are a role-player both you and your enemies should take scales according to your own whim. If the AI is playing with death scales it is your task to rid the world of him. It might also be easier to do than defeat the other pretender, a fertility god that has all his population with him in an orderly and growing nation.
I know that there are players that try to find strategically worthy opponents in SP games, but I believed, perhaps wrongly, that the SP community was more concerned with exploration and roleplaying and less with finding strong and weak strategies and ways to defeat an opponent efficiently.