Darka committed more than 10K CS so I don't know where that number is coming from. We have our homeland army(mostly courtiers and inner region lords) not go out to defend Eston, but my army, our non-homeland army, the Royal Army of Darka, did go out to help Eston. We weren't pulling out all the stops so it was much less then what we are using now, but it was still twice that of which you were talking about.
And even if we had brought 30K CS such as my army has now, I am not sure if it would have matter. Eston's army was in shambles, we didn't receive communications from their General for days and when we did it was just to sit around and wait. On top of that, as Perth said, the stalemate had been broken, so it would have been like trying to plug holes in a rapidly sinking ship.
