Urbans are by no means overrated, they are very good and you admitted yourself you've modded them out to make the game fair.
Overrated was perhaps a poor choice of words. What I meant is that Cohort I's and II's are more than adequate to get the job done. And making the game more fair was not for my benefit, but for the other AI-led factions.

3 units of town militia and javalin throwers against one battalion of hastati lose. even though i harass with javalins.
Town militia have poor morale and skirmishers do very little damage because of the high defensive stats of even pre-Marian Roman infantry. I forgot what the unit bonuses for the AI are at the "hard" setting, but this only serves to make an iffy situation even worse.

I'm assuming the battle you are referring to is the defense of Caralis? If so, your best bet is to not let the Julii anywhere close by chasing off, or sinking the invasion fleet. After you take control of Sicily (which you must do quickly before the Romans have time to ship units there), use your navy to the fullest extent until you get some of your more advanced barracks constructed. Once you get to the level of having Ellies and Long Shield cavalry, your job gets a bit easier.

The roster for Carthage isn't really all that bad once you get to Peoni and Sacred Band for your phalanx, Armored Elephants for 'line-busters', and Sacred Band cavalry. But the key early is the use of mercs on Sicily to oust both the Greeks and the Romans, and your navy.