Nerfs to Volibear are 100% deserved

He's been top of the charts for a while now. He's always been good, but with the inclusion of cinderhulk, a tank jungle item that gives clearing stats, and the shiny new CDR mechanic on his W, he effectively lost one of his biggest weaknesses as a jungler, that being that he didn't farm very efficiently. The nerfs help curb his farming power back down, so he'll be punished a bit more if he isn't able to make use of those strong ganks of his to gain an early lead.

However, Toplane volibear is actually struggling right now. It's never been a very popular pick, but toplane is still one of his meta roles. The nerfs to his W significantly cut down his dueling power in the early levels. This isn't good for a champion that already wasn't that good in the first place.

Perhaps, you could consider adding some compensation buffs to toplane volibear. Something to keep it from falling out of the meta entirely. Perhaps an armor/mr buff. These buffs would help him stay relevant in early fights, while also allowing him to clear healthier in the jungle, further solidifying his purpose as a ganking jungler.