Barbarians are strong in many ways. Firstly, their magic resistance. Secondly, they have very strong archers – cyclops. Thirdly, they have very durable units.
Plus, you need to add the retaliatory attack of harpies or the first strike of nomads. At the beginning of the game, this is the main strength of the Barbarians.
Added after 58 seconds
OptiMAL, maybe I'm wrong!