But like I said, the Tactical Cube is much smaller than an Assimilation Cube. It's not much bigger than the Descent Borg ship, it's clearly much smaller than an Assimilation Cube (then again, the Borg Cube from First Contact is also smaller than the Cube from TNG).
"Tactical" is meant for more immediate battle-actions, as opposed to "Strategic" which is more "Big Picture" and long-term (which fits the Assimilation Cube). This can be extrapolated to mean that the Tactical Cube isn't meant for civilization-assimilating like the Assimilation Cube, but for battles before that (to soften them for full-on Assimilation).
VOY had been augmented by Seven, and then by "One" the 29th Century Drone. That should make it capable of not dying instantly against a Borg ship weaker than an Assimilation Cube.
There was no need for the intrepid class to be up against a borg tactical cube for the sake of the story
The story required them to get onto a Borg ship. Would you have been satisfied with the crew pissing themselves at the thought of engaging a Probe ship, showing that they're utter cowards compared to Kirk, Picard and Sisko's crews?