Originally Posted by Ursa Arçadius
Singed and Volibear ultimately play a similar role, however Volibear is more about killing one target while Singed runs circles around the enemies slowly killing the lot of them.
The issue is that often Singed can kill one target better than Volibear, while still running circles around everyone.
And even worse, Singed can not only deal passive damage constantly, he can also just leave when he needs to. He has a better slow and range, Fling actually scales incredibly well with his AP (Voli's Q just doesn't get to scale, for some reason) and his ult is constantly up.
Some might say that Voli's passive heals for more than Singed's ultimate, but once an enemy is down to that low health you usually IGNITE them. Which just destroys Volibear. Whereas Singed will pop his at 70% health to ensure constant longterm regeneration.
He also has the option to just leave combat if it goes poorly. If you're not going all in as Voli, it's pretty easy to kill you. I actually run Ghost AND Flash on Voli to counter this.