The Doctor appears in Return of the Jedi

[NecronLord]

I recall scenes in sfdebris's review where the TARDIS has a viewing screen inside it, showing the outside world. Wouldn't he use that first?

For the record, the scanner used to be a major thing in most episodes of the old series, there fairly consistantly from the first episode onward. It was particularly prominent with the First Doctor, because he was an explorer far more than an adventurer but was used pretty regularly throughout.

It does still exist in the new series (Ten, offhand, used it in Army of Ghosts) but the Doctor seems to use it less.

Generally there's a downward trend in what useful bits of TARDIS technology get used.

The First Doctor had a button on the console that would electrocute anyone who touched it without disabling that. There were other defenses and devices (such as a control that blinded everyone in the control room temporarily except those who covered their eyes) shown through up to the fourth Doctor's run, when the TARDIS' defenses mostly disappear, and are in his run, more mentioned to dissuade villains than actually seen.

I like to imagine a lot of these defenses have broken over time.

[Parallax]

Doctor #7 wouldnt be dead if he had looked.

Have you actually seen the film? The console was broken by the Master, that's why he didn't know what was going on outside.

The Seventh Doctor is by far the most capable, and it's only an extremely unfortunate chain of events that led to his death. He can't be expected to use the scanner though, when it's something he has to repair later in the film, and he's in an obvious rush to try and recapture the Master.

The Tenth doctor did, relatively frequently, run out of the TARDIS without using the scanner, but you can't really apply that argument to Seven.

The 7th Doctor was scary in not only his capabilities but also his tendency to break the laws of times whenever it suited him (receiving notes from his own future self to alter his own past springs to mind) ... not to mention he was a manipulative bastard most of the time, thinking nothing of wiping out solar systems and entire fleets.
Mind-fucking his closest ally, Ace, just to take out Fenric was damn cold. Callously allowing the Daleks to blow up their own solar system and the Cybermen their own fleet. Laying schemes for foes before those foes even pose a threat or are even aware of the Doctor's existence.

It took a huge plot contrivance to take the 7th Doctor out ... and it wasn't even the shooting that did it. It was daft Human Doctors poking around his heart(s) and not understanding what the hell they were doing that did it.

Back to the actual topic ... Vader would be one of the worst choices to attack the Doctor. He relies on his cybernetics and suit for mobility and survival. The Doctor is extremely good at ruining such devices thanks to his little magic plot wand.

Hm. That reminds me. There is a Doctor Who novel called the Gallifrey Chronicles, the prologue is about the Doctor destroying a somewhat similar regime. The Doctor taking down a planetary space faring empire is used as the introduction rather than a piece of the actual plot. It lasts for ... three and a half pages.

An excerpt:

"Crallan!" He yelled. "Crallan, what in the name of the seven Systems is happening?"
His Chancellor ran into the room , already cowering, almost tripping over his dark grey robes.
"My Lord Mondova."
"What are my bodyguards?"
"They've fled, my lord."
"Scum! I knew they would be unreliable. That's why I had my Kyborgs built. Deploy them in the streets. Wipe out this resistance."
"The Kyborgs legion changed allegiance to the rebel, my lord. That's why the bodyguards fled."
Mondova hesitated.
"Then I have no choice. Call in the space fleet. Order them to atomise the city."
"The space fleet has gone, my lord."
"Gone? Gone where?"
Crallan shrugged. "We haven't managed to figure that one out yet."
"It is the most powerful space navy in the galaxy. It has snuffed out stars, Crallan. Civilisations spanning whole sectors of space have surrendered at the mere thought I would launch my fleet against them. It has campaigned, unbeaten, for over two centuries."
"No longer, sir. It's ... gone."

And, quite literally, the Doctor only arrived on that planet that morning. By the end of the day, Mondova's empire was shattered.

After that scene, the Doctor enters the Throne Room and points his sonic screwdriver at Mondova ... whose tech-armour simply falls apart and hits the ground, leaving behind a shriveled old man who has no idea what just hit him.

I have to assume The Doctor enters the situation with at least basic knowledge of the situation. He doesn't go in blindly, else that is what is known as stacking the deck. Similar to saying Marty McFly could beat up Batman ... if Batman was naked, drugged up, tied up, comatose and already suffering massive brain damage.