If Riot buffs Sejuani she will be back to being 70% Ban Rate
I'd say it's because of the amount of Utility she brings that dominates, I know most people would say NO to a kit rework (I'm part of those people) but if she did have one she could possibly be balanced out. But the fears of kit rework on Sejuani will be if she becomes to what happened with Sion where Riot destroyed his shield that helped him so much.