Toughness is a good feat that any defender should pick up. Also remember to take advantage of your stone's endurance racial power. Whenever you've marked a pile of opponents, activate stone's endurance for an extra 5 damage resistance per hit.
My other advice is to save your action points exclusively for your second wind. You're not a dwarf, unfortunately, so using your standard to second wind can be a little inconvenient. It's another ability that heals you and raises your defenses, however, and remember your Earthstrength ability gives you a big bonus to your AC when you second wind. If you get bloodied, go ahead and use that action point to second wind, then get in someone's face.