Why Sejuani feels bad to play now

I have played Sejuani a lot for several years and this is probably my least enjoyable time playing her. Old Sejuani was at least great for extended period of disruption where you could aoe slow multiple enemies. Now, too much of her power is in proccing her freeze for her E ability. She's a tank and should be in fights for extended periods of time. Unfortunately all of her damage budget comes in a single target spell with a longish cooldown. She should really have none of her power in her E ability and more of it moved to her W where she can put sustained damage on targets throughout the fight.