With the recent 
nerfs on the PBE I see tons of people saying "why cant she be overpowered instead of 
" and these posts are highly upvoted. Really people? How about we nerf whats overpowered/buff whats underpowered and you know... gasp BALANCE THE GAME??!?!?!
The people QQing like that are the bronze and silver players who want to do just that, QQ about the now and never look into the future.
It's not that she's being nerfed, it's that she's being nerfed less than a week into the patch. Riot can't possibly have enough data at this point to understand the full implications of Cinderhulk and the state of Sej. She could just be doing well because nobody knows how to counter her. She might just be legitimately overtuned with the addition of an item. Cinderhulk itself could be overtuned (I'm still not a fan of "+25% bonus Health." That just seems like a ridiculous ability.) The problem is we don't know which of these things it is because it hasn't even been a week, and Riot is immediately swinging around the nerf bat, while champions like Lee, Nid, and Zed have been frustrating players for months or even years and barely get an annual love tap.
The problem isn't that Sejuani is being nerfed. The problem is how hastily Riot's nerfing her. It's almost like tanky junglers being (gasp) dominant for once wasn't really their plan.
boards are stupid? gee wouldve never known
