Warwick was entirely magic damage before. How do you call that a nerf? If he were any of the champions in the game that actually itemize magic penetration then sure, he was nerfed by the shift to physical damage. Warwick was always been largely about abusing your enemy's inability to itemize against you, because even when building tank he does absurd amounts of damage.
The change to physical % damage means he is going to be doing more damage per "auto" against everyone except tanks. It also (kind of) makes Black Cleaver a "feasible" item on him, as his ultimate is a guaranteed 30% Armor Shred, where before he would have only gotten one stack from his ultimate (the % damage are each their own instances of damage, but his ultimate is a single source of damage)
I also don't think Warwick struggles in the new jungle. His hardest camp is the Raptors as you said, and they're not "hard" they just take a little longer. Autoing each of them once gets your dot going on them from your jungle item, and then by the time the dot finishes a second auto should finish them off. All in all he takes maybe an extra 5 seconds at Raptors, and the trade off is that his buff camps each have 5 seconds shaven off the clear time.
To be honest I've yet to experience the issue lengthened jungle timers have created. In mid-high elo it's almost essential that you take the time to clear Scuttle, and ward for your team especially early on. That's not even something that is unique to Warwick, every champion does it. If anything that makes his journey to level 6 not as rough, because now the enemy jungle can't powerfarm and gank multiple times before you're 6. Sure he's prone to invades, but frankly who isn't when Lee Sin and Vi are meta? I'd be lieing if I said that games haven't been lost before I even hit 6, but that's true for any farm-til-6 jungler and it's not something that is new to Warwick it's been a part of his "weaknesses" since 2009.
Regardless, this is all about to go out the window because Warwick is confirmed to be the next rework that is going to be released, and based on what they're teasing currently (with Singed's new lore) it appears they're going the route that "Singed created Warwick" which means we're likely 2 or 3 patchs at most until we actually see him on live servers.