Luna has 3500 HP and has a card what increases its HP by {200|200}. The problems with it are:
1; Bulldozer makes it total worthless. It has higher scaling than the champions HP because Luna is weaker than the champion and it almost always motionless, so its realy easy to shot it. But it deserves even higher bonus, just because Bulldozer can counter it well. Barik's Turrets' Hp can be buffed much higher scaled what makes it worth to use.
2; Add more HP doesn't helps a lot, because it makes its selfheal and Io's heal slower to heal it back to full HP. If it have higher HP than it still won't worth to heal it against bulldozer... (While the cd reducer card helps to reposition it and restore its HP.)
These are why this card is the weakest in Io's kit and it would be still weak with a buff. I suggest to rework it, what rework could solve all of the mentioned problems:
Feral Strength: Luna gains {8|8}% damage reduction.