I switched to lightning last night because I wanted to DPS and (especially because I'm widely known as a healer) I was chain rootlocked for 10+ seconds constantly and focus fired. When I even managed to survive for 10 seconds under such conditions, it was only because I was using everything else I had. I did not want to facetank; as a healer I am used to being able to neutralize rootlocking to a large extent, but when I was a DPS the enemy team decided I would be trapped in place and shut down and, lo and behold, I was shut down (in some warzones to the point where I did more "healing to full" than damage LOL).
As a sorc, I completely agree with your previous post that you quoted and with most of the things you mention in this one, but I can't agree with this part.
You were focused.
It doesn't matter if you were focused because they know you are a good player or because you were mistaken for a healer or because it just happened. The enemy team did what they were supposed to do: they recognized who is a threat in your team and killed you as soon as they saw you. They used their brains. And trust me, that's a pretty rare sight these days in PVP.
ANY DPS, let alone a light armor wearing glass cannon like a Lightning Sorc/TK Sage, should die easily if focused and shut down by more than 2 players of the enemy team. That's the whole point of being a DPS.
I understand your point wasn't that BW should make us immortal, but I just wanted to point out that this is probably a bad example.