Mail strikes a fair balance between Agility and Protection. Excels in neither, but fairly decent in both. The description of their defenses -
Warden's Cloak
Specially constructed for the night elves' wardens, these green velvet cloaks bear a fringe of deadly, razor-sharp blades along the hem, resembling the wings of an owl. Wardens learn to shift and swing the cloak dramatically, presenting the blade fringes to anyone who might get too close. The cloak is both a defensive measure against sneak attacks and a potent weapon for the warden when surrounded by enemies.It also provides numerous knife blades for the warden to use with her slicing torrent ability-
from
http://www.wowwiki.com/Warden doesn't really come off as a plate user.