I don't like the heavy emphasis on W in the upcoming Sejuani changes
It looks like there are some changes being made to Sejuani's spells on the PBE which have been posted here: https://twitter.com/ricklessabandon/status/535913487382642689
Basically, her Q got a ginormous damage nerf through the loss of her %ile damage with a marginal increase in base damage, and her E damage AND SLOW DURATION was severely nerfed in favor of spammability. In exchange, her flail spell got the %enemy health attack on initial hit (at the expense of base damage, and the %her bonus health damage was changed to % her total health damage.
Why is this bad?
On her W In the first place, I find her W to be a rather unreliable ability - you have to keep enemies in it for the full duration of it's spinnyness to get all the damage off - but there's a bajillion CC's and escapes in peoples kits out there, so you usually can't get all the damage ticks off before people are out of it. I get 2 levels early to farm, then max E and Q, since they're just better overall spells.
That thing enemies don't want to stand in now does more damage. WOOOOO!
On her Q
This had a massive damage nerf with no meaningful compensation. I'm sorry but increasing the base damage by 100 doesn't really cut it when 12% of the the lowest health champion, 
's (yes I know 
is technically the lowest, but that's only if he doesn't build HP, which no sane Gnar is going to go without) max health is 190, and that's on the lowest champion in the game. This is ginormous nerf against every other champion in the game. At the very least, if you're going to kneecap the boar this hard, you should drastically lower the mana cost to compensate.
Or to put it in more meaningful perspective, running down 
with your boar now hurts less. You can't possibly say that's a good thing.
Her E This is currently her best ability. At first glance it looks like lowering the cooldown and reducing the slow duration on this makes sense; it's less effective, but you can cast it more often. There have been times where I wished I had that Permafrost up a little bit sooner. The problem is, the lowered slow duration really hurts her now that you've increased the emphasis on her W - you know that thing you want to keep enemies inside of? Couple that with the damage reduction and this only exacerbates her existing early game mana problems, since you now must cast it more often to achieve the same effectiveness.
Doing what you did before, but for Twice the mana.
Her upfront burst It definately seems to have gone down - Boar Slam 160 (+40%AP)(+12% of enemy max health) + Auto Attack 100%AD + Spinny Flail 120(30% AP) (100%AD) + Permafrost 260(+50% AP) or 540 (120%AP)(200%AD)(+12% of enemy max health)
With the changes it becomes: Boar Slam 260 (+40%AP) + Auto Attack 100%AD + Spinny Flail (+12% of enemy max health)(+3% per 100 AP) (100%AD) + Permafrost 180(+50% AP) or 440 (90%AP)(200%AD)(+12% of enemy max health)(+3% per 100 AP)
I get that this is supposed to be an overall buff to Sejuani, but I'm not seeing it. Raising her base mana pool and lowering the mana cost on her W is pretty nice, and helps her out a lot early, but if you really wanna buff her, up the armor bonus from her passive. Early game she's just not that tanky.