Re: Borderlands 2 (Sept 18th) - 87 BAZILLION GUNS...JUST GOT BAZILLIONDIER
A lot of people aren't able to finish the quest. You go to Zed, it does his cutscene, then he tells you to go to Tannis and her cutscene is supposed to happen, but if it doesn't, then you can't finish it. It'll just say you spoke to Tannis but you can't turn it in. When you do talk to her, she just keeps doing the save Roland dialog.
But if you can do it in multiplayer with someone who hasn't done any of that, then you can go back to your game and skip it and bam, sidequest done.
Edit: Typically you can't go see Tannis at all until you see Zed because Tannis's cutscene will trigger if you walk into Roland's hideout.