Does not confer damage immunity. Rather, it creates a "+100% damage resistance" modifier against enemy attacks and friendly fire damage, which in turn can be reduced by other effects or properties, notably the 50% reduction in effectiveness inherent in all spirit-element attacks. Thus, this only reduces the friendly fire damage from a spell like Walking Bomb by 50%, which in this example still leaves the warrior exposed to an exceedingly-high amount of damage.
Combining this talent with other damage reducing abilities such as Barrier or Arcane Fortress will not increase damage resistance any further, as the property caps at 100%. Although most forms of damage can be prevented by hitting this mark, spirit element attacks will cut this 100% in half, thus ensuring the element will maintain at least 50% of its true damage without specifically wielding spirit resistance.