Defending Nature (DN) is the best skill on the Defender tree IMO. You cast it on a party member and it will essentially allow you to tank for them for I think it is 10 seconds now? Use it in the elemental dungeon when a Scout pulls aggro and you're unable to AOE taunt. Roha's Shelter (if that's still the same skill it used to be) is more of a PvP skill, or at least it used to be.