If you think a character in Kuroshitsuji is useless and unimportant, think again. Yana Toboso will most likely make that character have some super-cool ability and be a badass all over the place.
Exhibit A: Grell
Exhibit B: Phantomhive servants
Exhibit C: Elizabeth
Exhibit D: Undertaker (although I already loved him when he was his former idgaf self)
Just because one suddenly sprouts a weapon/fighting ability doesn’t automatically make them an interesting character. Just sayin’.
Last time I checked, “useless and unimportant” was under a different category to “interesting”. Say, the servants may not be all that fascinating, but they’re most definitely needed, particularly for that time period and Ciel’s… situation. (: