User blog comment:YourPrivateNightmare/Sejuani, the story, the problem, and the possible solution/@comment-25003900-20141105165655

I've played a decent amount of Seju jungle in her current state post SotAG rework, but never got a chance to play her before rework due to when I joined the game.

While I don't think she needs massive buffs personally as I've always had quite a bit of success playing her, I do agree that her passive might as well not be there at all in comparison to the passives on similar champions. Now when I say similar champions I intend tanky skirmishing champions that gank frequently. Honestly if I look at champions that are closely related in terms of how I'd play them, I come out with Maokai, Trundle, Vi, even Volibear to a degree, You find that each one has their own sustain, obviously you've touched on Maokai, but Trundle heals off of everything that dies around him, Vi has a passive shield that blocks 10% of her maximum HP, Volibear can basically kill himself and heal back to half health.

Don't get me wrong the free armor helps a little and I think 25 armor comes out to somewhere around 20% damage reduction assuming the enemy team has zero armor pen, but still, it's not that effective since a core item in every ADC is Last Whisper, a large number of champions build Ghostblade/Black Cleaver, so flat armor doesn't really do anything in terms of a passive.

I personally like your frost armor passive idea with the % of max health shield, it's nothing innovative, but maybe have it at a smaller % of health than say Vi, but in return for the lower % have it apply that attack speed slow that was mentioned.

I personally think that mitigation is a better way to go than a sustain because it's a little closer to her identity as a champion. She takes a beating and keeps going rather than she takes a beating and keeps healing. Since Sejuani is all about resiliance and overcoming hardships and such.