For a ProRes HD file, that sounds about right. It’s a lot different then standard def, I know.
As for uploading to YouYube, you should probably compress a little. If you have a huge file, chances are, your bitrate is pretty high too. YouTube plays 1080p at an average of 5 mb/s. If you compressed to 10 mb/s or even 8, then you’ll get a lot smaller “Web-Ready” file, and your upload time will also decrease.
YouTube will be converting and compressing your file to Flash anyway. It’s normally not great to show people a compressed version of your work, but when we’re talking about the web…you pretty much have to. Internet connections simply can’t play high bitrate files, especially ProRes files, so compressing is necessary
So I say compress first to an H.264 8-10 mb/s and do a reupload. It should look just fine on YouTube.