Sunfire Cape? That's back into his build order for the general masses?
The difference between Garen and Janna/Sona is Garen isn't forcing other options out due to his raw strength. 53% isn't actually that high when other options are still good. He is definitely strong right now, but I wouldn't say he is nerf worthy just yet.
The important thing to look at is why his win rate has gone up. You listed a bunch of stuff that he has been able to do for literally eight years, so I highly doubt any of it is contributing to his very recent win rate increase in a strictly causal way. The thing is damage and brawling are way up, which also means kite heavy compositions are down. Garen is just as strong now as he was when he last had his 49% win rate, maybe even less so now after the IE change, the only difference is people are not playing champions that are strong against him.
If his win rate gets any higher then I will admit, as a Garen main, something probably needs to be done, but this is a classic case of a meta shift changing which champions have good win rates. Nothing changed about him power wise, so if you really want to talk about what should be done with Garen leave the basic kit information out of it.