The general spec overview at the beginning of the Q&A was pretty spot on. It's easy for us to get momentum in PvE and lay down the damage, but the nature of PvP/arena doesn't really let us do that. Our long buildup time is harsh. We don't lend ourselves well to stop-and-go. We're pretty much all about the 'go' and a little bit of 'stop' sets us back to where we started. There's really no picking up where you left off. If the opposing team locks you down for a little too long, you pretty much need to start over. Your offensive momentum is irrecoverable. PvE usually doens't have to worry about that. Now, from this point forward, I'm going to address each Shadow-relevant quote point by point.
"Q: Since a lot of the damage a Shadow priest does builds with damage-over-time (DoT) spells, are you concerned about them being well-rounded enough to do adequate damage in shorter PvE encounters, 5-player dungeons, or in the Arenas?