Just for reference, at 45k spellpower 1k intellect is roughly 2% extra HPS BEFORE overheal. You need roughly 2.5-3k secondary stats to get to 2% more HPS as disc.
3000/600 = 5% mastery or crit. At 30% crit, 5% extra crit improves your HPS by 1.35/1.3 = 3.8%, with 15% overheal on aegis that is ~3.3% and mastery is pretty much the same value.
Basically even adding a raidfinder tier piece is going to be better than a thunderforged item if it gives you 4p-t15.
There is no excuse to not use penance on CD and picking twins is a bad example, because why do you want to be disc on twins.
You can be holy instead and 4 heal it.
http://www.worldoflogs.com/reports/r...?s=1923&e=2537
This was a pretty horrible attempt where everything went wrong and still we made it through because holy and mistweavers are so ridiculously strong. If I was disc here we would have about the same chance of surviving as a snowball has in hell.