I think if Tibarn were to find out about the blood pact, it'd certainly give him pause—but I'm not sure if that alone could convince him to give up his vengeance. Regardless of Naesala's motivations, half of his country's still dead, something something old-school sense of justice, arguably Naesala's had it coming for a while anyway, etc.

But knowing about the blood pact combined with considering political repercussions could certainly do it.