To me, the current state of stealth in WvW has a very similar effect, and sentiment I dare say, that allowing players to wp during combat would have. Stealth should only be allowed out of combat, to start a fight with an advantage or to sneak into position undetected etc. If it is to be allowed during combat (and it should not) then any damage taken from a hit or a condition should terminate it. Also, the start of any outgoing attack should also terminate stealth, including the finisher.