Giving the message while in PvP in addition to vs mobs may help sneaks some in PvP battles.
Furthermore, in extensive testing, it seems that an equal spot (+50) vs an equal (+50) hide (listen was very low for the spotter ie +10 and move silently was +50 for the hider) resulted in advantages for the spotter. the spotter sees the hider for almost 6 secs (1 round) before opposed checks spot vs hide are rolled again. This can be changed with a simple message to the hider indicating they have been spotted (an active hide check can be made at any time, thus negating the 6 secs a hidden char appears for).
In our tests, equal spot vs equal hide resulted in the spotter having a distinct advantage even though the rolls should be theoretically equal (1d20 +50 spot vs 1d20+50 hide). Also, the hider was visible for more than 1/2 the time.
Perhaps adding the message and making the max hide acheivable on the server = +5 more than the max spot acheivable would even things out?
Seems to me sneaks are the weakest class because they have no idea if their hide is working or not vs other players... thx!

