Whilst I would agree that the Borg were more apparently vulnerable whenever they were encountered by Voyager, the most recently broadcast Borg episode of Star Trek was Regeneration and was, in my opinion, a classic Borg episode.

Regeneration was an episode of Enterprise and I feel that it captured the feeling of earlier Borg encounters with the only-just-able-to-survive story.

The outline of the episode is that humans at a polar research facility discover the frozen corpses of several cyborgs whilst exploring the area. These corpses are those of Borg who were in the Borg craft which crashed in the film Star Trek VIII: First Contact. These Borg regenerate themselves and assimilate the humans at the facility and their ship, and leave earth to contact their own people. Enterprise is informed of this and finds the ship when they receive a distress call from a Tarkalean ship being attacked by the now-Borg vessel.

Enterprise rescues the occupants of the damaged ship but they have already started to turn into Borg and inject nanoprobes into Doctor Phlox in order to assimilate him also.

What occurs after this is a classic encounter with the Borg in which part of Enterprise is assimilated and they only just manage to get out of the situation alive.

Whilst a slight continuity error exists (the Borg were apparently first encountered by the Enterprise-D), this is explained by reference to the events of Star Trek VIII: First Contact. I feel that the episode was executed very well and had the tension of early "The Next Generation" encounters with the Borg.