You are going the wrong way with Garen, Rito.

Giving him a short-lasting tenacity bonus, so that good timing will separate good Garens from bad ones seems great.

But if you look closer, it's only up to Garen to time it for the moment when he gets hit by CC. Since vast majority of CC's has noticeable cast times, and Courage is instant, any proficient player will be able to always use it exactly the way they want.

This change does nothing to boost Garen in any half-decent level of play - new Courage has exactly as much counterplay as the old one (i.e. none), so even if Garen turns out strong, ultimately he will get nerfed to the ground after a few patches again.