How would you fix Warrior?

[Gamemako]

What if defiance also increased Parry stat by 20%

You could, but you'd be moving into PLD territory.

and using Storm's Path provided a shield that did the following

Remember that not all content is BC, so when you make changes that scale by a flat number, they're better in content with fewer people (where WAR doesn't need help) and weaker in content with many people (where WAR struggles). If you did anything with SP, it has to scale proportionally without a cap. Ideally, you'd make it scale exponentially (weaker early, powerful later), but that usually ends up broken with time and it's very difficult to implement.

//EDIT: I'm not saying current SP is any better, of course, being effectively a flat heal. Your idea would still be better than the current one in terms of endgame. However, I'm just saying that if you want to make an ability improve the stock of WAR, you should look squarely at endgame.