Qarthadast has not come close to being a challenge yet to me, because while tactically and qualitatively their units are awesome to face, strategically on M/M they are babies. The only army that stood a chance of actually annihilating me, a fullstack of iberian assault, general's cav, curisii, elite africans pikes and leebifeenikim, split itself up three ways to defend Baikor, Sucummurgi and Gader after my very vengeful Roman fullstack threatened all three simultaneously during my Second Punic War, and so they got thrashed in three piecemeal battles. I haven't touched Africa yet, but I foresee some challenges.