When you write that Rondo "disappears" in crunch time, which is the phrase that you used, for me to point out some of the other things he does to help the team down stretch is most certainly no straw man. It couldn't be more relevant to the discussion of whether or not Rondo disappears down the stretch of close games.
Clearly when I said he disappears in late games, I was saying that I don't appreciate hustle plays or defense. That's obviously a fair extrapolation.
What is a fair extrapolation? For starters, you obviously don't consider making big plays on defense or getting key rebounds or making key passes (for Rondo, at least) to be "stepping up". So I guess you appreciate them in the "they're nice plays to see but they don't make much difference in the outcome of the game, unlike scoring" kind of way. Or maybe I'm wrong, and it's more of a "I consider plays like that to be stepping up for players other than Rondo, much like passing".
Those are plays that happen in the flow of the game; they are reactionary. Obviously, they are very important, but they don't involve Rondo taking control and asserting himself -- imposing his will on the game.
In what ways have we seen this team struggle late in games, time after time? They fail to score; they take long jumpshots that don't fall; they stop attacking the rim; they have no inside game; the other team gets into the penalty and gets more free throws; the pace slows way, way down even when the Celtics have had the most success in transition / rapidly moving the ball earlier in the game; and so on.
Many of those issues could be solved if Rondo were more assertive, attacking the rim, keeping up the pace, continuing to run the offense instead of deferring to Pierce, taking shots as soon as he's given an open look instead of waiting to the last moment, and so on.