1. Actually explained at the end of the DLC. Click for spoilers.
2. Act 4 was short enough, I don't know if there were too many bugs. He kept breaking save games and occasionally there'd be a nasty crash when he was renaming the ending backgrounds or something. I think we went through seven versions in one day at one point.
3. Hunters are all about setup and combos, not spamming posts trying to race for the highest count. You can count on her to surprise, when it matters.