TNG Borg were too ill-defined to be anything more than a one or two story creation.
I'd have defined them totally BEFORE "Q Who?" was even aired.
And I'd introduce the 8472 aliens IN "Q Who?": Q would teleport the Enterprise into a battle between both of them with the Borg losing. It would show that they are strong, but they aren't the strongest.
That's another problem, Q said they were just ONE of many races out there but everyone assumed they were the number one Galactic threat when they were never meant to be.