The funny thing is, i´m right now playing a Sweboz campaign ( a must after that preview on EB2 forums! ^^ ), and Romans just exploded, invading everything in their reach within about 20 years: they even took Baleares! Now, you all should remember an agressive Roman AI ( mostly the Scipii ) in vanilla, when the Romans used to invade the hell out of Africa, and if one wasn´t quick enough Roman armies would swarm everywhere down to Sahara. The reason i mention that is simple: why the Carthage never does the same thing? I mean yes, they send pathetic armies to the coast of Capua, great..., but why don´t they use their navy as efficient as the Roman AI in vanilla used to, trying to reconquer Sicily back? ( a half stack Carthaginian army, led by a FM, is lingering on Sardinia for years now - and it´s war between Carthage and Roma!? - something wrong with initial diplomacy settings perhaps? ). Could it be the construction time/costs of the ships? Could it be the unit size of the ships per se? ( very low, so it doesn´t seems worth of building from AI point of view? ).
Last but not least, imho, the best thing to make Carthage really tough to fight against would be to take away those 2 ( at least ) Sahara settlements adding it to the Eremos province, block the passage towards Egypt ( like RTR used to do ), and tweak the ships a bit, though i don´t exactly know how... This would also have a positive effect: ( at least ) 2 new settlements could be placed somehwere else. That would be a great thing for the 1.3 fixes, and yes, i know, it´s all about EB2 for now, but hey - that project we all are waiting for might take another year, while those fixes might take just couple of weeks ( the community might offer some moding assistance, too, i think ).