If we compare them like that, then it turns out that almost everyone will defeat the Barbarians, but that's not necessarily true... :)
1) Fast castle construction
2) Low unit cost
3) No need to build magic schools (usually, levels 1-2 are enough for them).
4) They have a ranged unit of level 6.
5) And many other things, but I can't remember them right now...
Therefore, it's not a fact that the Barbarians will lose to the Humans; it all depends on how the player controls them!;)
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