Reign of Gaming

I don't play ranked much so I know my opinion doesn't really matter much, but I was just wondering why volibear is tier 5. I mean, all things aside, every support voli I've faced has done very well. Maybe it's just because I'm in a lower elo, both in ranked and normal, but it seems to me that a lot of people underestimate his support potential. His passive makes him hard to kill and so he isn't really afraid to walk up to you if make the slightest advance and fling you into his teammate. I was just wondering what your reasoning was behind it.