Noise reduction leads to very slow exporting?

I'm using FCPX's new Noise Reduction plug-in, over a 2.5 hour video. I have it set to Amount: Maximum and Sharpness: High.

Then, after a few other minor edits, I started exporting the project. It's taking a ridiculously long time -- I'm at 20% exported after 24 solid hours of exporting.

Is it normal for Noise Reduction to take this long? I'm on a 12-core Mac Pro; no two-hour export has ever taken me this long, so I'm wondering if it is something to do with Noise Reduction.