David,
How long did you foresee the final battle taking place over? Hour? Two Hours, half a day?
Also, I remember reading that the entire Tholian attack force sent to Vanguard accounted for roughly 20% of their entire fleet. After the Buenos Aries was lost, Khatami noted that roughly 65% of the attacking force had been eliminated.
So once the battle ended, most of the remaining attack force was eliminated. Given that the Tholians lost roughly a fifth of the entire fleet against one cruiser (not including the late comer on purpose) plus three other smaller vessels and a space station in that battle, would this be the reason as to why the Tholians never really engaged the Federation further (militarily) for the "Crimes of the Taurus Reach"?
Mike