So Riot, About Sejuani.

Regardless of if that 5 extra armour you tweeted about was a bug, it's quite clear that Sejuani needed it. As of this nerf she can't even clear the jungle properly. Her winrate has fallen sub 40% since that nerf and while there's a chance she bounces back a bit what would that be to? 42%, 45% in an extreme case, both of these numbers would be absurdly low for a relatively simple tank.

Sejuani needs to gain something from the preseason. She lost 12 armour from her armour quints which she needed since her last nerf and 15% AS from her reds. She only gained back 5 armour since your hotfix nerf gaining 0 AS unlike other tank junglers.

She needs to be given something. She either needs more base armour or some base AS to put her in line with other junglers. A solid start however would be to simply revert the hotfix as she seemed mostly fine before it. You accidentally got her to the right balance before "fixing" her.