The entire zone is full of hostile trolls from the vilebranch and the Revantusk. Not to mention the Forsaken forces at the research station. As long as the Horde holds Andorhal, Tarren Mill and the Sepulcher I think we can secure Lordaeron. And I am sure Hammerfall is still there too. I don't think Stromgarde alone can handle all the Horde alone.