Nightwish. Tuomas, Tarja, Anette, Floor.
Iced Earth. Greely, Barlow, Ripper, (Barlow again), Stu
The Ocean had a whole shitload, like 20 something.
I just don't think this is as big of a deal as you're making it out to be. Into Eternity has always had a lot of voices. That's kind of their thing. If anything's going to hurt them, it'll be basically disappearing for several years with no news on anything.