i like 
jungle. her ganks are strong af. probably the best ganker in the game.
her only flaw is her weak sustain in the jg and she provides no utility for the team.
her ult is good, and her Q is nice if you have a 
on your team. her ult takes forever to CD. honestly i dont think she's ban worthy though.
what team comp does fit with best?
Sejuani has initiation, a slow, and AoE ultimate, and does % health damage. As a jungler, she can provide a lot for any team comp, especially since she is so easy to pick up and play for anyone. Surround her with damage dealers and build her tanky, you can't go wrong, as she does well peeling for carries and locking down theirs. She's ban worthy because of how much she brings to the team without having to have challenger level mechanics.
NO UTILITY ARE YOU HIGH?!$!$?????!?!?!?!?!?!??!??!?!?!?!??
Here is all of Sejuani's utility: AOE Skillshot knockup gapcloser AOE slows AOE stun/slow ult Very tanky
I'm confused, your title read that she's not ban worthy, but then you go on to say that you like her.
You're just trying to get people to not ban her so you can play her or what's going on here?
