Number buffs are not what Garen needs (even if they're appreciated)
even if they are appreciated
Garen
Decisive Strike (Q) bonus damage increased from 30/55/80/105/130 to 30/65/100/135/170
Courage (W)
tenacity increased from 60% to 85%
damage reduction increased from 60% to 85%
Garen really doesn't need to be stronger when his cooldowns are up. His fundamental flaw as a fighter is that he is fucking garbage after blowing his cooldowns. Think if you really want to buff him and not have to keep buffing him annually (you can even look at his patch history, he gets buff after buff and still can't stay afloat. Same story with Nocturne) you should do something that lets him.. you know, do something after his spin is finished.
source http://www.surrenderat20.net/2018/04/424-pbe-update-even-more-tentative.html