I agree, this stacking order problem can be a pain

If say I have lineart, which must always be at the top, and then colouring shapes which must always be in a certain stacking order for say, arms, legs, torso etc, then what I do to force it is put each element on it's own layer [and if they need to be 'grouped' so they can be moved together, then use soft group which works across layers]

OF course, that can then have other work-flow issues because xara does not have nested layers; they have been requested, but the xara line appears to be that they are not necessary; however they said that about an eraser and an increased pasteboard size an both have come to pass.. so maybe one day