I used to hate the warmongers, but they're not much of a threat if you play your diplomacy right. Montezuma usually falls behind around the time he spams his UU (to the point where I had musketmen and he still had those swordsmen). Shaka declares war without reason but you can bargain peace with him after you kill some of his units. The true threat are the leaders that tech faster than me. People like Hannibal are who I MUST bully over early lest a gap forms.