Also, you should be able to play 100% offline on pc.
Here is a source:
" … but much as with previous Borderlands games you can play entirely solo if you want. Continuing the series’ trend, though, the game is much more fun when you’re blasting bad guys and looting crazy new guns alongside friends."
and this thread goes over how to do it. Seems people have success by turning off their internet connection while launching EPIC or the game?