I can't say much to Heroic Halfus as I haven't been that far.
I will say that you have two things that struck me immediately as far as gear and spec go.
One: Your spec looks fine, but take the points in Virulence out and put them into Epidemic. Longer diseases means a bit more damage reduction. Sort of assuming you had them in there from when you needed to spec for interrupts. Get rid of your DS glyph and grab up the DC glyph so that you're getting the maximum benefit from that CD. If you're using the DnD glyph for damage or aoe threat then I understand, but single target you'll want Rune Strike.
Two: What are you aiming for in your avoidance? Are you focused on Mastery or Dodge/Parry? If you aren't focused on one or the other, balancing them out will actually increase your damage intake. So don't do that. Maximize one or the other. Right now Mastery seems to be the better choice in pretty much all situations. This means that whatever route you go, you're going to have to consolidate your gems and move towards one side or the other. Going into heroic content you'll probably want to have a bit more health as well - you should probably have a bit more gear from the regular modes in my opinion.
Something else to think about: If you have diseases up on one of your targets already, you should probably just pestilence so that your next target will already have them up. They aren't as important as a DS however, you just need to get them up for your damage reduction.
EDIT: and you're missing one tinker.
Thats all I have for now.