Thanks for pointing out the relevant bits of Saint Joan -- I skipped most of the prefatory matter when I last read it.

My take on Henry VI's Joan is that she was intended to be portrayed as a villain all along, just a charismatic villain who makes some good points and has some nice speeches -- and probably the staging of the play at the time would have made that clear from the beginning, but it's jarring to modern readers who come in with different expectations.