Garen's in a REALLY bad spot at the moment.

According to LoLalytics.com (Basically Champion.gg for Diamond+):

"Analyzing 518 games played by the top 146 Garen players worldwide over the last 7 days. The average rank of the top Garen's was Diamond V. Taking into account win rate and summoner rank Garen is ranked 134 amongst all champions in the hands of an expert. Maximum 50 summoners are used per region with a minimum of Diamond V and 50 games played on Garen to be elegible."

Source: http://lolalytics.com/champion/Garen/ http://lolalytics.com/champions/

134/134. The weakest champion in the game at High ELO. And it's not like he's dominant in low and mid ELO.

According to Champion.gg, Garen's stats are quite mediocre:

Garen's got a 47.9% Winrate, and a 1.6% Playrate.

http://champion.gg/champion/Garen/Top

Even in Bronze Garen isn't particularly strong. He has a 50.1% Winrate in Bronze according to op.gg.

https://na.op.gg/statistics/champion/

Garen is statistically mediocre in Low and Mid ELO, and the worst champion in the game Diamond+.