My thoughts:
Tracked – any skills that would inflict Revealed would now inflict Tracked. The Thief is visible as an outline, but still retains all the benefits of stealth (e.g. health regeneration, condition cleanse, etc. if specced into Shadow Arts). It nullifies the advantage of stealth while not completely countering a mechanic that helps Thieves survive.
Revealed – Only occurs when the Thief attacks from stealth.