I don't know what majority you are talking about, but seriously, Captain America??? Why would he have ANY durability against Namor? Where exactly did Luke Cage beat Namor underwater? As for the rest ...
Namor was Marvel / Timely Comics' response to Superman. He was, for decades, simply the strongest character they had. Then when the Silver Age kicked off with FF, the Thing was introduced. Namor regularly took him on and beat him, but also sometimes lost, because of the his dehydration 'flaw' which kept him from being ridiculously unbeatable. Then the Hulk was introduced, and the 'title' of strongest of them all generally went to the Hulk -- except when Namor was IN THE WATER. And then Thor was introduced, and eventually, he challenged Hulk (and Namor) for the title. Of course, truth to tell, back then writers were more concerned about showing how characters reacted to situations and being overmatched or underwhelmed, rather than if they won or not. See Daredevil #7.
Nowadays, many writers either forget all this or just abuse and job Namor out to prop up other characters.
Here's a few of your requsted scans.
Here's Namor taking on both Luke Cage AND the Thing at the same time underwater -- and knocking Thing out of the water.
There's a great article, though I may not agree with every outcome he's stated, about every battle between Namor and the Hulk. Out of 45 encounters, Hulk has won 4 and Namor has won 4, and the rest were ties / draws / uncompleted. He's got a better record than Thor against the Hulk, who, according to this writer, has only one 2 of his encounters with Hulk. You can read it here:
http://hero-envy.blogspot.com/2012/0...b-mariner.html
http://hero-envy.blogspot.com/2012/0...b-mariner.html
Back in the day, in Avengers #3, Namor took them all on, and their roster included Thor, Giant-Man, Iron Man and Wasp. He took on the FF by himself. He took on the X-Men by himself. He's pretty much gone toe to toe with every heavy hitter in the Marvel U. This is why some folks don't find Namor taking on the Avengers successfully that surprising. I personally found it a bit much, at least with him holding them off with basically one hand each. But I also believe Aaron's Namor isn't himself. Besides the black eyes, and the Atlantean children fearing him, he'd never have done that Stingray.