Has Volibear Seemed Out of Hand Lately?
Not any more than any other tanky DPS champion.
Volibear's base stats are nothing special and his only defense in his QWER is his HP regen passive, which is kind of "eh" compared to a wide range of defensive skills in the game.
Any Voli issues are more a result of tanky DPS itemization being pretty solid at the moment over anything else.
to the point where he was kind of deciding team fights because of his big beef and damage output
Volibear is a fighter, he's supposed to be able to decide fights and he's good at fighting.
For the most part: fighters in LoL are pretty much carries that rely primarily on defense to survive long enough to kill things rather than relying primarily on speed or range to survive long enough to kill things. Or rather, juggernaut fighters are primarily defense: most fighters are more a mix of defense and speed.
Regardless: If a Volibear gets ahead, it's pretty much the same issue as if a Katarina or Lucian get ahead. Runs in, kills all the things.