Count Vendetta... LOL!
With Vader, we knew from the start that he was involved in Luke's father's death, so it wasn't a huge leap from that to what it ended up as.
If anything, I'd say the problems lie somewhere else entirely: If Vader was so notorious for choking his officers, how comes anyone in the Empire, like that hammy atheist guy in ANH, didn't "believe" in it? It didn't even make much sense in the original, but it really stretches SoD further down the line. Then, I wonder how much had "transpired" of the Emperor's own powers... lol. He was designed to be a powerless pawn at that point, though.
In case of Lando, the only problem is that they're stuck in space WITHOUT FUCKING FTL, and Lando just happens to hover around nearby on his gas mine or whatever.
That's a whole other problem, though - the shrinking of the universe, that is, in the LITERAL sense. STAR WARS HAS NO SENSE OF SCALE :D
That makes me wonder, is the SW galaxy anything like our galaxy? It's a fairytale on the far soft end of SciFi, after all, so maybe stars aren't that huge, and they're all more in vicinity of each other? After all, doesn't take them decades or years to travel between stars, right? ;)
The problem with ESB really isn't the "small universe"... however, the movie is kinda full of contrived coincidences. First, the rebels escape the Empire and the Empire fails to track them... ok... Luke finds Yoda on Dagobah... ok... ahm... HOW THEY LANDED IN AN ASTEROID WITH A DINOSAUR IN IT??!! How could it breathe??! Okay.... um.... there were like several Destroyers hovering around, and TIEs and shuttles were available constantly, so how comes the Falcon could hide on the surface of the ship??
Then, some robot smashes C3PO... WHY? The only reason I can think of is that it was supposed to foreshadow bad stuff... that Bespin was a crapsaccharine place or whatever... but... it wasn't really, the Empire had taken over like 2 days ago.
Then, what does Boba Fett does at Jabba's palace? Ah whatever, he's on his payroll I guess... whatever. The entire way they smash up the monsters and escape, having all planned ahead and stuff, makes litte sense if you think about it, as well.
Just one thing I wanted to say about the "small universe" concept - of course, we all know how unrealistic it would be in real life. But it's what fiction is made of - what if some sort of fate, or invisible patterns, help us move around and bump into important things and people by "accident"? When things like these happen in real life, people usually ascribe it to "synchronicity" or treat it as improbabilities.
In fiction, however, a story might make a point out of exploring the concept of fate and mysticism (like Homo Faber), or be an escapist fairy tale that fulfills our desires and simplifies the world (as is the case with Star Wars - it also deals in fate, of course) - it can also be done with humor (Back to the Future, Austin Powers 3; arguably Star Trek XI) for pure fun... because the plausibility of three Biff Tannens walking into a bar and mobbing three McFlies across 3 centuries is absurd, so the audience gets that and enjoys it as a funny spectacle.
Point is, despite the numerous contrivances and plot holes in the OT, I think these "shrinking universe" revelations played well into the "mythical / escapist" zone, despite creating some logical problems - maybe due to the charming execution of it all.
The ones in the PT, maybe with minor exceptions (I don't really care about Padme knowing Palpatine, that was kinda just unnecessary), however, fall strict into the "silly fanwank" category. And no stylistic apologetics are to drag them out of that pit.