I don't mind the back up singers that much. I'm surprised by the overwhelmingly support for these back up singers. I can respect that for the duo. But to get back to my original question, does Furthur need them? Here is a list of aging bands that don't NEED a back up singer(ps I listened to a show from 09,a soundboard where they had no backup singers, and they rocked that shit. Link below)
String Cheese Incident
LET JK SING MORE!!!!!!
To answer your original question, yes, I think they help make Furthur the band they are.