Opinions on Bone Dancers?

[Crake]

It seems Bone Dancers are more accepted in 8v8 groups. I never played one or grouped with one, for any material amount of time.

For people that have:

Are Bone Dancers good in 8v8 groups?
What is main responsibility of Bone Dancers - purely for interrupting opposing casters?
Is there a steep learning curve to playing one well?