I'm very sorry about the lack of downtime notice and patch notes posted here on the forums. I had the info that I was supposed to post, but after the chaos of Extra Life, it fell through...
The Defiance Public Test Server is now live! It's running the latest Arkbreaker build, so if you want to get a hands-on preview of the DLC, you can do it right now.
The PTS client is a completely separate thing you need to install, but yes owning the game through Steam counts as owning the game, so you'll be able to play it.
There's no need to put it in the same place. The PTS client is basically treated like an entirely different game - you download the installer, patch it up, and log in using your Trion account.
Sorry - I'm talking about the issue that can cause a major arkfall to get in to a state where it doesn't come down even though all four spikes have been placed.
The only version of the game that came bundled with the Season Pass was the Gamestop-exclusive "ultimate edition" of the game (the one that came with a messenger bag).