Naxx 10 or 25? Not sure if it makes any difference as I haven't been to 25 mans yet, but you really don't "have" to be at 25k unbuffed health to MT Naxx 10. I've got 5 Naxx drops (2 tier pieces) and still not quite there yet, and I have no issues there.
I would say that you are fine to be MTing Naxx 10, if that is indeed the one you're talking about. Again, not sure about 25. And your trinket, the Seal ... /jealous :)
One thing to add to the list right off the top of my head is Arcane-Shielded Helm from Heroic Nexus. That's also a very good, and very easy to get (barring ****-poor luck with the RNG), piece of gear. Enchant stuff, even if it's not the uber enchants like 22 stam to boots, but something is much better than nothing. Use borean kits if you have to.