Make it do physical damage now that garen has top tier shred along with darius (ideally it should just be always true damage considering how gimped it is compared to Darius ultimate if the target isn't the villain).
It sucks ass when you try ult a carry who has maw or scimitar, and it sucks super ass trying to ult a tank. Point being, it sucks ass unless it is used on a specific 1/5 of an enemy team that garen or may not even be able to get to depending on who it is.
But seriously, Garen can ult a tank that might have like 500/2600 HP or something and it does less than 300 magic damage LOL.
And no, don't suggest that garen get a void staff for stronger ults xD