You will want Sith Purity.
Lots of nasty dots and roots (like from sentinels) are physical. You'll want to be able to cleanse them, and keep in mind that your cleanse is one of the few heals you can do while moving. But it only heals when specced.
Empty Body also helps your survivability by a surprising amount. Rather than having a self-heal on a 30 second cooldown be 15% more powerful, put that point in Empty Body and heal yourself for 4/8% more all the time. And yes, that boost to all healing received applies to Unnatural Preservation as well.
I would take 2 points out of Seeping Darkness to make these changes (You have Recklessness for when you need crits), and 1 point from either Dark Resilience or Sap Strength. Or possibly only take away 1 point of Seeping Darkness and get rid of both DR/Sap Strength.