[Suzerain of Sheol]

Well, it's been a while since I read it, but the Silm. probably has a fair few expendable characters, and yet... the stories are very disconnected a lot of the time, meaning that people who serve no purpose in one tale are central to another.

And the Fall of Gondolin, as I said takes place over a long time and involves many different characters.

Turgon, the king.
Idril, his daughter.
Eol, the Dark Elf
Maeglin, Idril and Eol's bastard son.
Hurin, who inadvertently guides Morgoth's forces there.
Ecthellion, who leads the city's defnese.
Glorfindel, who leads the civilians out of the city and fights a Balron on a cliff-side.

And one other important character that I can't recall at the moment.

So... maybe not too many, but I could be forgetting others, too.