[Opinion]: Sejuani ganks are easier. Overall teamfight damage lowered.
https://www.youtube.com/watch?v=YEwQ_5GNKPA Video now added. Time stamps there for easier views.
So I have a very pretty Sejuani game that I have recorded that eventually (if I ever figure out how to convert WebM) make its way to YouTube. That being said, here's how I feel about her.
Early level clears: If it wasn't for having 400 damage from level 1 (yes 400) on her passive, her wave clear would be really bad. That being said. Birds and Krugs are harder to do earlier in the game since you cannot passive the smaller monsters (or E for that matter). Solo monsters are easier only because of the extra amount of chain cc that can be done against them allowing her to heal vs them the first two seconds of her armor passive.
Ganking: Ganking, I will admit, is EXTREMELY easy here. I was a little wary prior to playing her but in fact having 3 forms of hard cc make her near impossible to get away from. I only failed one gank entire game. Albeit mainly due to getting a little cocky.
1v1: Mid to late she can easily 1v1 most champions. Nothing has really changed there. What has changed, however, was her stickiness to that champion. With W applying a slow on top of stacks, Sej is now the only champion that can apply 4 types of cc from ALL of her moves. I wasn't originally aware of the slow on her W but that combined with her Q and freeze, she is actually now stickier than Skarner. That being said, he damage output is significantly lower too, which makes sense.
Team fights:
This is where I personally feel she's lacking. Where as old Sej could easily freeze all 5 champions, she now only applies an ashe affect ult on the enemy team. This makes it harder to pin down groups of enemies. Also, you cannot use your E on the champion you initially ulted. Unlike Skarner, who could chain cc with his ult. If you want to chain cc you're actually going to want to save your ult for mid to late fight. That is the only time you can freeze an enemy twice in a row with no cooldown; E > R. Applying her stuns to multiple champions is also tedious, but I imagine that was the idea. Braum's passive is better in that regard. Also you will find her passive only lasts two seconds, so don't expect to be as tanky as she was in the past in prolonged fights.
Overall:
While I was not particularly happy they changed Sejuani, this change was actually a good change. Something Riot frequently fails to do on something like this. Even though she lost a lot of tankiness and overall damage, it was more than made up for in stickiness and utility wise. She's the first ever damage dealing utility tank in the game, making her an extremely hard champion to stay away from, especially in a 1v1 mid to late game. 9 out of 10.