Just about everyone I know can do a passable Yoda impression -- I have a different idea what the lines should be since "Lead them down the darkside it will" is just nonsense and dishonesty masquerading as wisdom (and I'm agreeing that's the reason provided in the Saga -- I just call nonsense on that reason).

I'd be all for this addition if a better reason for lying can be employed.

Second, if having Maul/Grievous is counter to the whole concept of the Sith and it's "Rule of 2" then what are Vader and the Emperor talking about when they repeated say Luke will "join them?" They don't say "replace one of us."

Clearly there is no rule of 2 from the Sith point of view. Maybe the Jedi believe there is, but that's just more confusion, apparently.