JDotter, Hum why did DnT do PST. Well i'm sure it's for a number of reasons.
1) We found multiple bugs which we reported and some of them have already been fixed. Nice not to have to deal with them on live.
2) Might as well learn the fights doing pts a few hours here and there so we can continue raiding just a few nights a week even after it launches.
3) It's sometime new to do and new things are fun? Why does anyone ever join a beta for any game out there most of the time the answer is it's fun to try new things first before it goes out to everyone.
4) I don't speak for the guild so I'm sure there are more reasons the above are just mine.
Did we spend a lot of time on the PTS? If you go back and look at our steams you might be surprised just how little time we put in. Due to a few people being a bit casual we had very little time with our core group in pts. An example is this week we got a whole 4 hours in. We had a whole 3 hours total with our core on the Council fight the entire pts that does not seem like much to me.
^pretty much this.
Why would we do something like NiM TFB where we've seen and run it in various forms for over a year, when we could be on the PTS running something fresh and new? In addition, it's a good time to learn new fights and to identify and report bugs.
Though I'd like to point out that the PTS is not the only thing we did this week. We also went and did NiM S&V because it was fast and then did PTS afterwards.