Theres probably a strong reason the goblins never survive, such as their such a weak race that they would be killed of AFTER world-generation anyway.
Weak in what way?
Humans are (supposed to be, as I understand it) a fractured civ made up of independent city-states. However, they also spread damn near everywhere.
Elves cripple themselves by deliberately using inferior materials. They are also frailer than humans. Yet they have exclusive access to Good regions among the civilized races, giving them a safe-haven within which they reproduce in vast numbers, leading to the zerg rush phenomenon.
Dwarves, as we clearly see in Fortress mode, frequently struggle to keep peace within their own communities. Even if this is not unique to dwarves, they are still smaller than either humans or elves and thus weaker in combat, despite their stocky build. A major strength to dwarven civs is their access to superior metals (e.g. steel).
Goblins are as small as dwarves yet not as stout, but they have exclusive access to Evil regions. Ethically, they are much more compatible with dwarves and men than with elves, so while elves tend to fight everyone the goblins are often at peace with their neighbors. If you aren't fighting, it doesn't matter how well you fight.
Each race has its strengths and weaknesses, and will continue to distinguish themselves as Toady develops the game. The lack of unity among humans, for instance, should have a much greater effect on world gen and gameplay as time goes on.