The Iron Fist build is a blast I highly recommend it for PVP. If you you plan on tanking reg ops and HM flashpoints it is also viable, although heat management is a bit harder than a PVE tank spec.
I'm also having trouble with tanking this fight. The pylons move around a lot sometimes and I'm having the very same issues. Also there is a bug where some times the shield does not break even if it hits him square on the dome.
I had poor performance on my laptop this weekend it has Vista and 2g of ram. I highly suspect adding 2g would do wonders.
I got windows down to using about 800MB on my laptop. Currently on my desktop Swtor is using 1.7g.