while this works when you have a fully developed army after many turns, just charging your militia units en mass into a bigger army usually doesn't work in the very beginning. Try using your strategy on vhvh while blitzing in four seperate directions as Venice, south to sicily, east to byzantium, north to HRE, and northwest to France and you will see that you will often be outnumbered crazily and are forced to fight strategically.