Agree with sad before..

But the real key to heroic victorys ( I have my map flastered with x-es = places of heroics victories ) is not odds, but the number of engaging troops!!!
You may have, lets say 100 (number, not units) elephants and the enemy 2000 spears and cav...

The odds may be close, the victory willl be heroic!!! Trust me!!!

So:
have a (numerous) SMALL, but ELITE army!!! and search for terrain appropriate for def.... or off... battles ;)

And you will also have your map filled with x-es

The odds do matter, but empiraclly not as much as numbers ;)