Grishka: I'm curious-do you mean soprano in the sense of choir soprano? Because AFAIK the songs I find easiest to sing in operetta are the mezzo roles; Clementina and Adah. As Tattie Bogle said and I've found, my notes below the staff are easier than the ones above. (According to StageAgent.com, Clementina is a mezzo) And the best thing about my voice is the middle range.
Herbert seems to have loved stratospheric sopranos, didn't he?