I've played game with hecarim as enemy jungler, and I was in bot lane as a supporter
He is a pretty good ganker, his e makes him a lot easier to gank(and also ult), it's basically like rammus without a taunt. But in team fight he doesn't seem too good. He's basically like nocturne. His ult speed makes him very fast go in and initiate but because it's too fast their team won't be able to follow him that fast which sometime causes him to die before his team can even reach it