As far as I´ve been able to tell, you can´t get MotH´s from city battles, neither offensive nor defensive. At least I have never gotten one during my campaigns. Oh, and I´ve gotten a MotH from battles were the odds were in my favour, so that the odds have to be 1-3 is perhaps a bit off, though i am by all means no expert.
I do remember a Greek campaign in RTW though were I experience a sudden burst of expansion, I had 3 very good general with very good armies all situated near several almost unguarded enemy cities. In 20 turns I took something like 15 city´s, and after that I couldn´t fight a single captain led battle without getting a MotH. At least it allowed me to pick and choose.