Well, yes, in a battle of pure physical strength, the person who relies on speed and weaponry is at a disadvantage, that's kind of the whole point of strengths and weaknesses. And as for Sabia dominating orcs who are physically superior to her, it's more of an honor/fear sort of thing, orcs don't fight barehanded, they use weapons, and if this orc knows that Sabia can kill him with ease if they were both armed, then he respects/fears her and thus follows her demands if she is able to utilize his feelings properly. Again, Big = Good and Small = Bad is not how you should look at this, use a bit more thought to think about why things are happening instead of going "small woman dominate big man?! BAD!"
If you played a Dom Sabia, you'd know she more or less performs better than the minotaur against Kira, enough that Kira sends the minotaur to set up the camp and prepare dinner, so in a normal fight, it's likely that Sabia and the Minotaur are AT LEAST evenly-matched, the minotaur even begins showing hints of respect towards her at the end of his quest if you're playing dom.
As for Kia/Neve/Kira/Levtruv(Or whatever his name is), they are stronger than Sabia, sure, but that's only because they're exceptionally powerful when compared to other characters, wouldn't be much of a game if Sabia was the strongest warrior to have ever lived.
You either only played a quick sub playthrough, or you played the game without reading anything, I don't know what else to tell you.