Awhile back I looked into the reports of dispatch always applying the debuff even if the brigand missed. I tracked it back to the setup of the double up spell. Some special scripting was done so that this spell could work properly. However, at the same time the person who did the scripting forgot to return if the attack landed or not. Normally the melee attack effect handles this and returns false so that extra portions of the spell like dots on the assassin or swashbuckler debuffs don't land. So since it currently doesnt return a false the additional effects always apply. This will of course impact pvp because they don't have to worry about hitting but will always debuff you regardless.
The tricky part is that fixing this will likely have some sort of impact to pve as well. I don't want spells that work one way in one fight to be totally different in another so this is something we are discussing and how we can minimize the pve impact. The issue is noted though and it's something I am looking into.
LINK