Lombard Berserkers are great when/if you fae large infantry armies, such as WRE armies. They should provide you with plenty of targets, meanwhile you should have cavalry enough to deal with their cavalry. Sit back and watch.

I have had my fun with Berserkers, but the most important thing to do is to keep them back initially. No need to let htem get pasted by cavalry or archers.
If the enemy tries to oppose you in the streets of a city, then these guys really come into their own. Even bodyguards will suffer badly to them (provided they do not get their cahrge in).