Guild Wars 2

Awwww bummer.

If those don’t stack, why bother at all with lightning? Saving grace for me with lightning were those stacking move speed buffs. All those move speed things are arranged as if they were meant to be combined to create one cool Flash-Build.
Signet of air seems a waste of a slot. And Zephyr’s Speed is basically always a waste if one choses to take a buff with more than 10% move speed (which overwrites it). This seems kinda not thought trough…

So I started leveling up my Elementalist and putting points into lightning and arcane to get all those nice move speed traits and buffs.
But somehow I rly can’t notice a difference…
I have/plan to get:

Zephyr’s Speed: Move 10% faster while attuned to air
One with Air: 25% bonus movement speed wile attuned to air
Windborne Dagger: Move 15% faster when wielding a dagger
Signet of Air: 10% movespeed buff

Can’t think of anything else.
My question is: Do they stack, what stacks with what and if not, why the heck don’t they tell me?
If Zephyr’s speed (which you get automatically) does not stack with “one with air” then why chose this trait? wouldn’t that be obsolete?

I am realy confused with movespeed seemingly not increasing although I skilled all the traits. Help and Explanation would be welcomed.