It's a bit much. Just remembering the names of 11 major characters ( with the addition of minor characters ) asking a lot from your reader.
Depends on you, the theme of the book and what you want. It's your book.
In an average sized novel, is killing off 11 major characters a lot?
Having 11 major characters in the first place is a lot, so killing them off is yeah, a lot for an average sized novel. But then again it could depend on whether the book was apart of a series etc. In general, and in my opinion, yeah I think killing off 11 major characters is quite a lot.
In my opinion, getting rid of 11 major characters in a book is a lot. As a reader, I would be wondering what the point was in killing off / getting rid of so many characters. To introduce so many people and then jettison their existence into space would completely flummox me and make me wonder if I should keep reading the story or not.
Instead of getting rid of them completely, you might consider other means of them disappearing from your story, such as a move to a different city, attending a summer camp, going to college, etc.
I've found this link helpful in my writing:
First ... ARE they "major" characters?
I mean, do they have detailed backgrounds?
If not, they aren't a major character.
As to killing off so many ... the most I have seen killed of in a single novel was 8. Even though most of them weren't main characters, they had been part of the main character's entourage for so many books in the series that everybody (readers) "knew" them. In that case, the original writer died and the "ghost writer" had to figure a way to end the series. They did so by killing off everyone.
Sure.
Two movies based on books with an extensive list of characters are The Great Escape and The Dirty Dozen.
The Great Escape is a 1963 American World War II epic film based on an escape by British Commonwealth prisoners of war from a German POW camp during World War II.
The film is based on Paul Brickhill's 1950 book of the same name, a non-fiction first-hand account of the mass escape from Stalag Luft III in Sagan (now Żagań, Poland), in the province of Lower Silesia, Nazi Germany.
The Dirty Dozen is a 1967 American war film directed by Robert Aldrich,[3] released by MGM, and starring Lee Marvin. The picture was filmed in the United Kingdom and features an ensemble supporting cast including Ernest Borgnine, Charles Bronson, Jim Brown, John Cassavetes, Telly Savalas, Robert Webber, and Donald Sutherland. The film is based on E. M. Nathanson's novel of the same name that was inspired by a real-life group called the "Filthy Thirteen"
Major or central characters are vital to the development and resolution of the conflict.