Yea she's been picked in LCS a lot lately, but so have other junglers with good mobility and cc (Skarner, Gragas, Rek'sai, etc). But with Sejuani cc is literally the ONLY thing she has. She offers absolutely NOTHING in terms of damage. And as far as her cc is concerned you can qss/cleanse out of most of it so it's not even that good. TLDR PLEASE do not nerf Sejuani. If anything she needs buffs. She's so weak in her current state it's crazy.
Actually no I'm wrong. She's not THE most overrated champ (that title goes to Yuumi), but she's definitely in the top 5 for sure.