Do any of you people have a caster or scout class? Wind Walk works the same way as any invisibility spell or stealth skill. The higher your ability, ie: app1 to master, the higher level the mob is you can go by without it seeing you.
While 'invisible', just stray away from mobs that still have a red outline around them. Otherwise, they can't see you. If you're getting tired of not being able to get passed a few certain mobs, go find or buy the next level or two up of the ability from your own.
Maldibion - Najena - 21 Coercer
Isheek - Najena - 20 Monk
Terra - 10 - Bard