Stealth cannot be achieved whilst either in combat or stood too close to any enemy.
Any ability with stealth is good for the element of surprise, but if you buff your stealth stats with clothes, you'll effectively have less melee damage buffs, to use against an opponent. If you choose not to buff your stealth however to add more melee damage to your Karate, people can see you easier, thus rendering the exercise somewhere near superfluous. The common trend seems to be for knife thrower coupled with stealth, rather than any Martial Art.
Like most things in MxO, swings and roundabouts
Hope this helps