Drinking a Giant Strength potion and invisibly throwing Orin off the platform doesn't work any more; it just says "Target is Blocked" But what you can still do is...
Pick up Orin and throw her at the Sanctuaried Bhaal cultist on the left, who will get knocked off the platform and then Orin and everyone else will be surprised. Text appears saying that apparently even Bhaal himself is surprised and the usual cutscene does not trigger. I'd be interested to see what happens if anyone tries sneaking the rest of the party invisibly to attack her as she lies prone, because she doesn't shift to Slayer until her initiative if I'm not mistaken.
