Without logs, screenshots, in-game video recordings, my non-streaming client install w/ all the optional content (adventure packs, voice-overs, etc) takes less than 14GB. Using Test will double that size.
You can probably save some space by backing up your log files, and screenshots and storing them elsewhere, but 80GB of space would make me believe either you have a large in-game video capture, or add-and-remove programs just isn't reporting the size correctly.