When Dirk went 1-11 or whatever it was in the first half, I would argue that he was not leading his team, and that if not for Jason Terry shooting the lights out and several other players playing extremely well that they would have lost. (Dirk said this himself in the post-game). But overall, Dirk did lead in the playoffs. He shot only a slightly lower percentage in the playoffs than he did in the regular season (49% to 51%) and he shot much better from beyond the arc (51% to 39%). Contrast that with Knight shooting 32% in the tourney and 42% in the regular season, and 33% from 3 in the tourney and 37% in the regular season.
Luol Deng shot 54.2% in the tourney and 47.5% in the regular season.
jj redick shot 40.5% in his freshman tourney and 41.3% in the regular season. Less, but not by much.
It would be interesting to me if you could find a good player in the NBA who, in their freshman year, had a 10% drop-off from their regular season average to their tourney average. Of the people you have mentioned so far, only Redick has shot less (and only .8 percent less).
It is becoming less and less likely that the drop-off in Knight's performance was the typical result of the circumstances of a competitive environment (in which most players actually play better) and instead is becoming more and more likely that he simply ended his season on a fizzle.