Both. Just like with the Cowboys defense where they had a lot of strengths but a clear weakness that specific teams were able to take advantage of. For the Cowboys offense to dominate a defense, which they did numerous times, it again requires the ability and personnel to take advantage of a team's weakness and for the team to have said weakness.
Now for this years playoffs EVERY single team can claim at least 1 bad half for their offenses (SF can actually claim 1 bad half for their offense in every single game it played). The thing that made the Cowboys defense unique is that they were only two teams, the other being the Eagles who were floundering the last 2 months of the season, in the entire playoffs who can claim they had a unit that was bad an entire game.