Why nerf Sejuani?

Sej has always been a strong pick for competitive play as shown by her win rates being pretty consistently high. She has an incredible amount of cc and is an awesome initiator for team fights. However, the nerfs Riot gave her this patch have pretty much dumpstered her. What was the point? She was already under a 50% win rate in platinum and above last patch. She's now stuck at around a 47% win rate in all divisions. I like playing Sejuani a lot, but I might drop her and swap to a stronger jungler like WW because she feels so inconsistent to play now.