His buff was back toward the end of season 2 when they improved his ratios. The new items for season 3 are just very efficient for him. The new black cleaver should be called the armor blender when Garen buys it. Health, cd reduction, and armor shred on physical damage are made for Garen. The new spirit visage is also excellent for garen packing a large amount of MR with more cooldown reduction.
With his itemization improved, Garen is more formidable opponent at all stages of the game.
Oh yeah, SotD active on Garen's Q or E is rather nasty, and the new Atma's builds out of avarice blade which helps Garen build that gold quicker. His build is just very streamlined right now.