Agreeing with what HeatEdgeSword said, I think Serperior and Kyurem-B shoud rise to Tier 2 and Tier 1 respectively.
Kyurem-B has very powerful stats in general, having a very solid bulk and a decent speed tier, outpassing threats like the Oricorios, Kommo-o, Heatran and Lando-T (If not scarf)...