What i don't understand is that Syndra is getting some buffs rather quick after release.
But the Sejuani players have to wait for maybe even a year before Riot finally takes some action.

Really Riot... Whats taking so long?

I had the most success with support Sejuani. If you manage to survive her weak early game you can become a beast late game. Her ulti can be awesome if the team takes advantage of it.

However i recently picked up support Volibear and he turned out to be even better in setting up kills for the carry.
I'd like to see her buffed so she at least becomes good at jungling

The problem with Sejuani is that in most cases she is very weak, with the exception of late game CC. But she doesn't do much to help your team get the advantage early on. She can jungle, she can slow, but she just isn't quite good enough for ranked. Riot won't comment on whether they will be doing anything with her, but they do allude that we are all idiots for claiming she isn't good enough.

Here's how you make Sejuani viable, two easy steps.

1: Give her a defense steroid of some kind. Maybe a percentage buff to resists, maybe an a health shield. Just something that lets her actually tank! Perhaps it could scale off targets affected by frost, and activates with your E, or how about with your Q, so you can initiate/escape better pre-6 or when your ult is down.
2: Reduce her Blue dependance - that means shortened cooldowns and reduced mana costs. Right now she can barely donate the buff to the mid lane.

Thats's it! Success! Sejuani is viable! Not overpowered, or weak, but definetly viable!

I haven't seen a single post where anyone from Riot will post that they will fix her, they don't even acknowledge that she needs work. Well maybe ricklessabandon, but otherwise no one does. They all act like she is perfectly balanced.

She is picked ~.7% (not even a full 1% on any given day) in ranked games over the last month.
She is picked ~1% in normal games.

There are 105 champions, so that means the average for ranked games is 9.5% since 10 unique champions have to be picked. .7% is far below the 9.5%

Edit: I want to point out that all of the top bans are picked more than Sejuani, making her even less likely to be picked. And the 9.5% doesn't take into consideration that 6 champs can't be picked.

For normal games it is a bit more difficult because 10 unique champions must be picked on draft and duplicates can be picked in non-draft unless all draft are not included or are included in ranked. I don't know the stats for draft vs. non-draft. So let's assume they are equal. That means the average is 7.1%, and she is 1%.

Being in the bottom 5 (draft and normal) means there are over 100 champions picked more frequently. That means there are 100 champions that should be looked at, evaluated, and buffed after Sejuani is fixed. Top 5 perhaps evaluated for nerfing balance, but many don't need to be nerfed, many are just favorites. Sejuani however is not a least favorite, she is simply not good enough to be played more than 1% of matches.