Have the cleric get a rod of Reach. Also a Spring-Loaded Wrist Sheath with a scroll of Breath of Life and/or some First Aid Gloves are good.
I like the superstition rage power. You just need to make sure your party has a chance to buff you prior to combat or raging.
Headband of Havoc is a godsend for Barbarians. Being able to enter a Rage as an Immediate Action once per day allows you to Rage when it's not your turn, which gives you all the defensive benefits of your Rage before you get smacked with something. Headband of Havoc also allows you to consider one of your Rage powers to be 4 levels higher, which works really nice with Superstition, and you can change that 4 level higher benefit for any Rage Power and on a per- Rage basis, so you can change which Rage Power you want to be higher every time you Rage.
Also, get a Flawed Scarlet and Green Cabochon Ioun Stone (8,000gp) and get the Internal Fortitude Rage power to get fatigue immunity and allow rage cycling before you're level 17. Rage Cycling is really important for getting off your Rage Powers that only are allowed once per Rage more frequently.
In my experience, it gets harder in higher level play.
Your DR/- is stacked at lower levels, but as you get higher, it becomes irrelevant unless you start layering defenses. Miss chance and the like are your best friend. Shield Other spells are nice, but only as long as the HP battery you're hooked up to can handle it (AoE spells are the bane of this combo though, so be careful). Saves too. I like Superstitious, but make sure you are buffed before you rage. People conveniently "forget" you need to save against all spells while raging if you have it.
On the other side of it, your damage output needs to be through the roof. AoO's, pounce, etc. Anything you can do to attack as often as you can is worth every ounce of gold. My invulnerable rager used a reach weapon with lunge and pounce. Opening with a lunging pounce through a reach weapon was pretty serious, since he could get a full-attack from across the map and position himself where he was only getting hit once when fighting a medium creature. Against large/huge, he was able to close without provoking an AoO (which helps with the above). The goal when I played him was to remove at least one foe a round, starting with casters (that's personal preference though).
Hope this helps!
Take Stalwart and Improved Stalwart at level 11. This should help keep your DR relevant. This requires Endurance and Diehard, but you can get Endurance from a Scarlet and Green Cabochon (make sure it's flawed, so you can also rage cycle), and you can ask your GM to allow you to retrain Raging Vitality for free (since Diehard does similar things).
I also second the idea of miss chance, but note that a minor Cloak of Displacement will compete with your Cloak of Resistance, so beware. You'll generally be fine as long as you don't run into a lot of creatures with 2-handed weapons and possible power attack. But on the plus side, such creatures are usually putty in your party wizard's hands.
Make sure to grab Combat Reflexes + Come and Get Me at 12. It'll greatly help you against melee threats. Pairing it with stuff like Pushing Assault is great too.