Humble, any particular reason you prefer to top rather than jungle on WW? Is it just so that you can go with a non-smite build, or do you think WW is sub-par in jungle compared to the other popular jungle champions?
For starters, I've been guaranteed a kill at level 6 every time in lane. Were as with a jungle warwick that isn't always a guaranteed. No one sees the danger of a warwick that instantly hits level 6 if they are near half health or lower. Ult + Ignite + Q = 700ish damage at level 6. It WILL kill anyone (except gangplank that eats off the ult or someone with cleanse). Best part is you can even do it on their tower. With Warwick's passive and Q I am going to be at 3/4 healths or greater most of the time. So when I reach level 6, as long as the person is in lane and low life with me there they are dead. Tower hugging won't save them. I can ult straight on to them from out of range of the tower. Which means I take less tower hits because I don't have to traverse manually towards them. The other great thing is now that I'm killing them, it activates the blood hunter passive which gives me the speed boost I need to get away from the tower fast enough to not die.
As for jungling, smite is needed for really any sort of decent speed in the jungle until you can get a madreds. Which is a nice summoner spell, but it is limited in some regards. I have used smite to steal quite a few baron and dragon spawns. But in reality the NEED for it after the first 6 levels is drastically reduced. The amount of times I had the situation to steal either baron, dragon, or a buff is about once every 4 games or so as a rough estimation. It just doesn't occur that often. Flash and ignite are used damn near every team fight. They are overall way more useful throughout the game.
But warwick pre-level 6 ganking from the jungle is silly at best. Which means most successful ganks from warwick won't happen until level 6 or later. Which narrows the window for good gank attempts from a jungler. A good jungler should at least have a chance at a gank at level 3 or 4. Master Yi, Nocturne, Rammus, Nunu, Amumu, Nasus, Fiddle, Shaco, and Xin for example all have some form of CC and/or gap closer prior to level 6. Warwick does not. While he has arguably the easiest time in the actual jungle, he can't gank for squat until level 6 with any form of reliable success.
To me taking a solo lane or a duo lane works wonders. If doing the duo lane, I start roaming after level 6. Again his gank potential with ignite and ult are ridiculous right now. If the target is half health they are dead. If they have more than that they are still dead as long as the person in that lane you are ganking for comes to help kill.
If you watch most of the high elo players that play warwick, very few of them play him in the jungle anymore. There are just better junglers than him.