I'd argue that that kind of time for loading a file would be as a result of the processor de-compressing or re-constructing the file into main memory, i.e. taking raw(ish) data and turning it into a model. 25-30mins would allow for 90GB of file transfer at 60MB per sec which the WD7200.10 can do.
I'd be surprised if it were generating 90GB files.
This may be correct but the, unfortunately throwing more cores at it doesn't seem to help. Maybe a threading issue. How can I test this?.. Log HD re-writes during load??.