Goblins are short and puny with below average stats and their weapons cause lighter damage compared to an Orc's falchion, but they have strength in numbers, and pretty much are the only race who's cavalry are warbands and not individuals. Fluff wise, I think the Blackbloods would have used the Goblins as "first wave" troops, sending hordes of them to soak up the first hails of arrows.
Jase