This build seems great imo , I will try this out , will rate later. I like how you bring out the Offensive Approach on Garen with Infinity Edge late and A Brutalizer , something similar I use on 3v3. Just to remember , Garen isn't a tank , he's a fighter champ , who can semi tank small 3v3 fights , but True Tank do his job better. The only things I don't really like about this build is getting Ninja Tabi , since you lack magic resist in your build early , but it's great synergy with your runes and masteries imo.
Oh and starting with Doran's Shield. Giving some reasoning to me would be great . Thanks !

thx pandaroo

Definitely an improvement- good job

i've updated it! check now

I think you might want to reconsider your offensive masteries and switch the AS masteries into CD masteries. Also instead of that 1 point in AP Offensive mastery you definitely need the exhaust mastery.