I guess Riots balance guidlines don't count for tanks.
Sejuani
Winter's Wrath (W) - W1 max health as damage lowered from 2% to 1.75% - W2 max health as damage lowered from 6% to 5.25%
She's far from any pick/ban/win thresholds in soloQ and while she sees proplay, she's not exactly pick/ban or overly dominant there either, just basically the only viable tank jungler. So why the nerf? Sure, it's just a small one, but still, it just feels like some random hate vs tanks from riot.