there's no reason whatsoever as to why he'd expect to have a fight.
He might not expect it, but he certainly would have been prepared for it.
"Right lads, we're gonna go in here, level one of Lorgar's greatest works, embarrass and prostrate him in front of his legion, and I'm pretty sure he won't lift a hand against us. Not sure about Malcador though. He might get it." Sorry, doesn't work for me. By his very nature he'd have come up with several plans to counter any action Lorgar might take within seconds of being given his orders. He wouldn't be able to stop himself. Things like that are at the very core of his being.