Just a suggestion, invisible/stealthed opponents should lose their invisibility/stealth if they are hit by an opponent (takes at least 1 dmg) or if they attack a target (deals at least 1 dmg). This might help solve some of the thief problems in WvsW.
Since this will be somewhat of a nerf to the thief/stealth class, their initial attacks while stealthed should be buffed to compensate.
Another way to compensate is to have the stealth recast reduced and duration extended, if this is implemented.