The fine writer of comic books and other things, Kurt Busiek, has this to add to my piece on why the X-Men comic was almost certainly not an imitation of DC's Doom Patrol…
In addition to the stuff you've pointed out, I can't see where someone thinking the Doom Patrol was a cool idea would decide that the bits to copy were the wheelchair and the name of a group of villains.
The Brotherhood of Evil and the Brotherhood of Evil Mutants also debuted the same month, which would make it even harder to swipe, even if either party thought it'd be a good idea. I mean, I can see someone thinking, "Brotherhood of Evil is a great name, I want something like that," and inventing the Monastery of Menace or the Lodge of Licentiousness. But just adding a word to a name the other guy's using is…pretty obvious. Not to mention that everyone involved was more creative than that.
And if Goodman wanted another book like F.F., as he did, Lee and Kirby didn't need to hurry-up and swipe a book that had just come out. Kirby (if not Lee, as well) had been reading pulp S.F. with stories of mutants feared and hated by ordinary people, fighting against worser mutants to save the world (and themselves) in the form of Kuttner's Baldy stories (which featured bald telepaths, even), Van Vogt's Slan, Sturgeon's More Than Human, Shiras's Children of the Atom…they had lots of other material to draw from, and they'd even both done stories about mutants before.
Some people have pointed out that the X-Men's blue-and-yellow costumes and the Doom Patrol's red-and-white costumes have a similar design — but the X-Men had theirs first; the D.P. started out in F.F.-like coveralls.
It doesn't make any sense from the POV of a creator.
It sure doesn't. And something else I might have emphasized is that folks who did comic books back then rarely read what their competitors were doing. Devout comic book fans read everything but don't realize that most comic book creators didn't and probably still don't.
I have no trouble believing that Stan Lee hadn't seen The Fly from the Archie company before the creation of Spider-Man. Heck, an editor at DC Comics almost never read the books supervised by the other editors there, even the ones with whom he shared an office. Publishers looked at their competitors' sales figures and would sometimes order up similar books because of that.
There seems to be an ongoing debate among some historians as to how Martin Goodman at Marvel found out that Justice League of America and before that, Challengers of the Unknown were selling well for DC. There was this fabled golf game between Goodman and Jack Liebowitz at DC in which the latter supposedly bragged about the numbers, prompting Goodman to race back to his office and tell Stan Lee he wanted a super-hero team book.
That golf game almost certainly never occurred. Goodman never said it did and Liebowitz said it didn't. What I think happened was that someone asked Stan how they came to start Fantastic Four and he said something like, "Oh, Martin found out DC had this book that was selling well. He probably had lunch with Jack Liebowitz or played golf with him or something," and the part about playing golf became enshrined in Marvel history. The simpler explanation is that the sales figures were no secret. Anyone who cared could find them out…and DC and Marvel then had the same distributor which made it even easier.
Here's what Goodman's company would put out when he saw the numbers on Pine Comics' Dennis the Menace comic and Harvey's Casper the Friendly Ghost…
He did not find out they were hits by playing golf with anyone. And that kind of thing came from someone looking at sales reports, not someone looking at a competitor's comic book and saying, "Hey, that's a great idea for a comic! Let's steal that!" There might be an exception somewhere in history but that would be rare.
And to some extent, what was happening here was not theft of an idea but an attempt to confuse buyers into purchasing your knock-off instead of the other company's real thing. It was like all those records in the sixties that hoped the customers would think they were buying The Beatles when it was actually The Beetles or The Fab Four. Anyway, thanks, Kurt.