The Tactical Cube is smaller than an Assimilation Cube, and the designation "Class 4 Tactical" implies it's also weaker.
Funny thing is, if VOY was always able to put together armadas and they always got wasted by the Borg in every encounter, and all of VOY's Borg stories were the same except they had an armada at their command, no one would complain. The quality wouldn't matter, the number of cannon fodder ships getting trashed would redeem those stories.
The Cube in "Q Who?" and BOBW was something meant for taking on entire civilizations and assimilating their important worlds, a "Tactical" Cube by comparison is going to be for tactical battles BEFORE the major assimilations happen. Softening them up for the Assimilation Cube's major attack.
The real problem was overpowering the Borg so much, making them so numerous along with the overpowering, and being lazy in not better defining them earlier on.