There isn't enough cold damage for it to be useful and the 3% max health that goes along with it is negligible. It would be nice to see it tweaked a little bit. What if the increase to max health was merged with Robust and an increase to cold damage were added to Resist Frost? No class has cold magic skills but spell crafting is coming in the near future and an increase to cold damage would give Nords a small advantage in crafted frost elemental spells. Maybe the name of the passive could be changed to Blood of Atmora or something like that to reflect the change.
Robust: Increase health regeneration in combat by 10/20/30% and increase max health by 1/2/3%.
Rugged: Reduce incoming damage by 2/4/6%
Blood of Atmora: Increase cold resistance and increase cold damage by 4/7/10%.