Nephthys
The Gr8est!!!!!!!!
Hey, plot or no, it happened onscreen, and that's what we have to deal with. Do I think its bullshit? Yeah, but I accept it.Not one time. There was also right after when the TIE barreled into Vader.
ROTJ, when Luke went apeshit, Vader was surprised.
Palpy, he didnt sense Vader rising up against him.
Look, I'm not saying its perfect or anything, but unless its completely blindsided, overwhelmed or just not paid attention to, precog does tend to work, and isn't nearly as fail as you're trying to make it out to be.
All 3 of those came in exceptional circumstances, Vader was looking around for who had just shot at him, he'd just found out he had a daughter and that it was actually someone he'd personally tortured (plus, he wasn't surprised by Luke but by how much power he suddenly gained from going berserk on his ass), and the Emperor was completely focused on the last possible threat to him broken at his feet. Exceptional circumstances, when the characters were at their most vulnerable and weren't properly paying attention. CIS, which won't happen here.