Is Steady Stance 4 just a better steady breath

Nope different effects completely. One has guard, the other has speed up cooldown when getting attacked.

No, it's the opposite of Steady Breath. Breath +1's your cooldown. Stance 4 -1's the enemy cooldown.

They fulfill different functions. Steady breath is for double-edged play; steady stance 4 is for defensive or passive play. If you want Surtr to sit there like a boulder and be extremely hard to kill, use steady stance 4. If you're someone like Selena who's hard to double anyways (which is why you would want steady stance 4 - preventing your opponent from hitting you with a special) you might prefer the extra special charges.