Both are in the same battle on the first turn of battle after my unit has self cast Noble Legacy. The tooltip for my unit generated by mouse over of the initiative list portraits does not show the hit point benefits from Noble Legacy, however looking at my unit's detailed stats on the unit card, it shows that the Noble Legacy benefits have been applied. I'm not sure if the benefits aren't showing in battle tooltips because the battle is using unmodified stats, which means that Noble Legacy is worthless, or if it's just a UI error.
Edit: The tooltip shows the Noble Legacy effect, but has not applied the +7 hit points my sovereign should have. That's why his hit points in the tooltip are 91, but on the unit card are 98.
Maybe it's a mechanical issue, but this method for applying Noble Legacy seems clunky. Why not have a persistent effect?
Either way, there's a bug here somewhere.