I would say the Borg are the worst
kind of enemy from a storytelling perspective. If you make a bad guy too
powerful, then you constantly have to find a way to weaken them for our heroes to win. After Wolf 359, the Borg should have swarmed
the Federation with cube ships and pretty much taken it out, essentially ending Trek. Instead, the Borg continued to send in just one ship at a time to be beaten back each time.
Sure, we can try to justify the Borg's refusal to go full-out on the Federation on an idea that they don't think the Federation warrants more than a single Borg ship, but that's really just an excuse to keep the Borg beatable.