By heavy do you mean the weight of the character? Less up and down movement will fix that. Your vimeo link is quite short so I didn’t get a good look at it to critique. Really I’d suggest posting something up here you are working on and we will give you some helpful tips.
I would say just bring the back up where the spine is. If you don’t have a spine, i would say delete all armatures and extrude from it to make parenting a lot easier (love the model). Also with the bone for the head set its parent to the spine and under parenting in armature data click inherit rotation, inherit rotation, and inherit scale if not already checked.
If you are as good as you say you are at animating, then the problem is probably in the rigging.