Yes, there is a lot going on when Shield Wall is used.
The cooldown is long for an Arms or Fury warrior when compared to our others abilities, trinkets, items, and potions. As a Protection warrior, they have the passive ability Bastion of Defense which lowers the cooldown by 3 minutes. Specialization design idea, who knows.
Damage from a one handed weapon as an Arms warrior is less than Fury's Single-minded passive.
Is it enough to fight back with CS, MS, OP, and Slam? Pummel, move, Execute?
Who knows what is enough and what isn't. When should it work, and when shouldn't it? How can one say for sure?
#showtooltip is quick and I enjoy the swapping mechanics of the warrior class.
/cast shield wall
/equipslot 16 sword
/equipslot 17 board
Disarm, Dismantle, Psychic Horror, and Voidwalker: Disarm. All of these disarm both slots now a days, Main hand and Off Hand.
Disarms don't last very long as a Warrior with 4/5 Gladiator's set and it's effect can be trinketed or Bladestormed.
It's nice to be able to anticipate a Warrior's abilities and prevent it by disarming him, however, when fighting multiple opponents the damage can be hard.
As an Arms warrior, being locked out of Recklessness or Shield Wall is bull!@#$.
A Fury warrior, I believe they can swap into Shield Wall and swap out of it to 2H x2 while keeping the aura, so that's understandable.
I think it could work just like Deadly Calm and Inner Rage has in the past. Just /cancelaura either one of them and swap to the other because they will not work together.
/cancelaura blade storm
/cancelaura deadly calm
/cast inner rage
/cancelaura inner rage
/cast deadly calm
As for percentages and cooldown time, it's hard to say what one ability like this needs when we have a lot of other damage reduction abilities that can be used with it, who knows.
You use the word outdated, which implies to me that it has not kept up with other classes because some of them can use defensive cooldowns with no reduction or delay in damage and just keep going.
E.g. when fighting a warlock I have to look for a little aura icon that lets me know when they are taking -40% damage, Death Knights, and Rogues too, can use defensive abilities and just keep going.
When a warrior goes defensive: Defensive stance animation - no rage gained - 3 second cooldown, weapons changed - global cooldown, Spell Relfection animation, Shield Wall animation, Demoralizing Banner in the ground - hit the binding then click the location, Die By The Sword animation alert, and it all takes a lot of global cooldowns, time, and action.
I do enjoy how it feels though, the swap, planting a banner in the ground, the sound of Shield Wall, Die By The Sword animation not so much, but, it's all pretty great.
I've been playing an Arms warrior forever and I have some kind of an apathetic view of it all, so I just keep playing no matter what is changed and find my way. Let Blizzard do whatever they please, i'll play the game my way and find what I enjoy. There isn't another game like this one.
Win/loss become meaningless and only the fight matters, dying a good death is more important to me. Looking at your corpse after it all and cheering, saying something like: Hell... as far as I know, I took that fight to the limits of my knowledge and abilities, I just can't imagine what else I could have done! ...Woo!