You have six games on Hecarim. Heck, I won 16 of my first 20 games as Lulu, which is no indication of Lulu being strong. Hecarim at Plat + owns the second lowest win rate in both Top and Jungle. It's a simple fact. People with 50+ games on Hecarim are only getting a 47% Win Rate on the guy. You'd at least hope for 50% when you actually know how to play the guy.
Sheen took a hit with the loss of AP. Not that big of a deal for people that didn't build Sheen early on Hecarim for the spellblade, mana and AP. Some of us did.
Swift boots recently took a minor hit with the loss of 5 MS and price increase. That's a hit on Hecarim's passive which translates to his damage output. That hurts his early game, since swift boots were easy to complete early on.
Dead Man's Plate was a nice buff to Hecarim when it was introduced, but has taken some minor nerfs with price increases and diminishing health values.
Zephyr was removed, which was an item some people used on Hecarim.
As for Hecarim's kit... his base health and health/lvl was nerfed. His perma ghosting through minions was removed. His base mana and mana/lvl was nerfed. These are minor nerfs, but clearly have added up to where we are today.
I'm 6W/7L with Hecarim, though I admit I've tried so many different (and stupid) builds on the guy. I even tried a Runic Echoes build with him just to see how the MS boost would amp up his damage. Then they nerfed Echoes. ¬.¬
Thinking the next time I play him, I'll run
+ whatever else makes sense against the enemy (more MR, more Health, More Armor... whatever). I know he's not the best tank, but if you give him Gauntlet or Mallet, he can deliver item based CC effectively with his Q.
I also want to try out the
combo on him at least once. I doubt it will work, and even if it does it would probably be a fluke. Still would be fun to try.