Every character but especially the villains were one dimensional in the early days, for me Magneto simply evolved, Claremont give him consistency and the reason for figthing, in the process it made him one the greates antagonist of all time but the original tale still happen, of course, less loony and less sixties references but the core theme can easily be adapted to modern times. The original brotherhood is still the one with the twins, Mastermind and Toad, plus the retcon of Astra that doesnt affect the original run.
For me isnt hard to imagine Magneto killing for the greater good of Mutankind, even if that victim is a mutant, you perfectly described him as a villain.
The original discussion is how problematic is understanding a character when each run dismiss the previous character development.
For Doom, i dont consider him a better side of Magneto, ultimately he is practical, he will help the heroes if something bigger comes to rule but at the end of the day, his endgame is him as the Earth dictator. Doom War got Doom for me, at least thats how i view him.