Not "new," but not exactly what I would consider super experienced, either.
That being said, I was talking about allying city states in general, not specifically a diplomatic victory. The victory seems fine, but I've genuinely thrown my hands up at trying to keep any CS allied. Playing as Venice, with Statecraft's and Freedom's influence-per-turn and watching their missions I STILL couldn't even keep my closest neighbors allied for more than a couple of turns at a time.