Low CPU utilization on FCP X export

I'm trying to "Share" a video on youtube. It's a 1080 25fps.

Currently, the Share Monitor says it's: "Processing: Transcoding", so this is not related to upload speed.

If I do a simple "Export to Quicktime", the video is done in less than 5 minutes. After one hour in "Share Monitor" it's about 70% done.

The CPU seems under-utilized, as shown in the stats from iStat Menus:

*) Temps are fine.
*) Fans are running slow (I never manually touch fan speeds)
*) compressord and FCP are only using less than half the processor.
*) The CPU+FSB use less than 70W, but the W3520 have a TDP of 130W...

Any tricks from the pros on how to get compressord to actually use the resources available?

Or is it "just" because when I do the "Export to Quicktime" the video is about 12GB in size, whereas the YouTube is only 1.8GB? So it's two entirely different tasks?

(Previously, when doing videos for youtube, I normally do the "export to quicktime" and then let Handbrake do the compression, but with this social stuff catching on, I thought I'd try to use the built-in function)