Assassinate bugged

[Syrophir]

For some reason assassinate gets aggro before making DC check for kill from sneak. Impossible to assassinate encounters that doesn't have aggro on someone else or been bluffed first.

I have to use sap bluff and assassinate or let them aggro some party member to kill my target.

[Blakelore]

I have ran into this as well..
Thought it was just some epic ward in Kings Forest at first, but then after using it in quests and other explorer areas ( like vale ) it always failed, unless something has drawn agro... like a summon, hireling ... or even a party member ( like those party members give you time to sneak up on something anyways.. :-) )