Volibear, is too strong.
Volibear in season 5 is incredibly strong, with the stat buffs and all of that. He will become a strong pick soon, that will dominate everything. He has everything someone wants, a very strong sustain passive, a gap closer, a attackspeed buildup and huge AD damage nuke, and a powerful slow. On top of that he has his own statikk shiv!
Volibear has to be toned down, with just blade of the ruin king and tanky items he deals tons of damage while being so tanky. Volibear's passive regeneration should be toned down by a quarter, while making Volibear's base movement speed lower. His base health should be toned down by 27, and base health regeneration is halved.