Another thing to try (I havn't tried this yet) is to use a WRAP deformer.

Basicly, you surround/cover your group with similar-shaped geometry that is ONE peice, like a cylinder, etc. then read the docs on how to treat that as a WRAP deformer, so that when you paint the weights on your WRAP geometry, it smoothly deforms your grouped stuff as well

Not sure if that'll work, but its' worth a try right?