You seem to be forgetting that the Borg have thousands and thousands
of cubes, and a total lack of reluctance to sacrifice their forces. Even if it comes down to a war of attrition, the Borg have the obvious advantage.
But the characters in the book have no way of knowing that these first 11 cubes are only a lead up to an all out invasion.
We the readers know because of information released regarding upcoming books.
None of the Starfleet personnel should know what we know except perhaps for Picard.
For all everyone else knows, the 11 Cubes were the sum total of the Borg attack and all is right with the galaxy again.