is powerguard useful should i max it out im not sure if i should

You could've just checked some guides you know...
Well, Power Guard is quite useful.
When maxed it reduces the physical damage you take by 40%, and reflects it to the enemy. (Essential for Hp warriors).
It's a potion saver really.
Unless you're going to be a hybrid page/fighter, you end up maxing it anyway.

in other words...max it

in other words...max it
If you can.

At higher lvls and when you have higher defence, it becomes somewhat useless though.

(Well yetis and stuff)

Max it as your last skill, you might as well, warriors have enough sp to max everything except both boosters and both masterys. And it will be useful when your level 90 fighting grims.