His E is what is holding him back. W and his Passive can be better.
His passive is only really strong in the early game (Warwicks early game is terrible) or when he is ahead. Pretty much nullified with any MR item. I want his old passive back from season 1.
W is good but it needs something else. If Warwick was a more recent champion I guarantee you it would have some passive MS or penetration on it.
His kit has awkward scalings on almost everything. Passive scales off level, Q scales off AP, and ult scales off bonus AD, while W and E are used more for utility for your team than for yourself. So you are pretty much forced into a tanky-ish role unless you get like 10 kills in the first 8 minutes of the game some how. Design flaws because this is not how "fighters" are designed to work at all. He is outdated, and I wouldn't be surprised if he gets relaunched like Trundle down the road.
Warwicks big issue is his powercreep problem. Too many champions do what he does but 500x better. Completely unviable for competitive play. He is still decent in solo queue, but then again so is every champion.