Here's link to check T4 skill simulator
Some people choose windwalker because she can fly but in new updates, windwalker can't fly anymore, spirit shots cannot be used until the character touch the ground (so sad to hear this) :'(
but i'm still choosing windwalker tho
Multishot - Good for spamming , not bad damage , can attack knock down targets. Lv 16 is the last big % damage boost
Tumble, Power tumble, Aerial Evasion, Mind Conquer - all max. mind conquer (mana regen) really needed for windwalker because having spiral kick maxed really drain your MP
Moon kick, Pin Wheel, Somersault kick - Moon kick helps to reach ground fast/ prevents getting stuck in the air when eagle dive and spiral edge at cd.
Somersault kick for double somersault combo
Physical mastery, Mental mastery - extra points go here, increase hp% and mp% (not really important)
Magic arrow - not really needed but i take for long range spam, sometimes can be really useful in pvp
Wise of the Owl , Rage of the owl - increase critical rate 50% and critical chance 10%
Blooming kick - increase 10% stun chance every lv , i decided only to put it at 1, u can put it on lv 2 or 3 for increasing stun chance
Eagle dive, Circle Shot - great damage but lack of sp, so i let it stay on lv 1, but make it lv 2 or 3 wont be bad as long u have sp
Chain trampoline, Tip top, Shortbow mastery - max to shorten the cooldown.
Shortbow mastery for increase attack range and damage
Spirit Excellation, Spirit boost - max
increase agility in big amount, spirit boost for longer use time
Double Somersault - this really useful at pvp 1vs1, if u like pvp and have more sp, just put it here (option)
Cyclone kick, Spiral vortex - both are archers main skill, great damage, max!! Must max!
Hope this can help, any comments are acceptable :)