I agree with you 100% re: mixing generic styling (i.e., the bar height/color) with the actual data-driven attributes (the bar width). The styling is just inlined in these demos because I wanted something that worked immediately out of the box from a single file. In production we use SASS to generate CSS styles for visualizations.

The question of how to separate data-driven attributes (the top/left positions for points on a scatterplot) vs. incidental layout considerations (the ordering of bars on a bar chart or grid positions of small multiples) is something I've been thinking about for some time. Ideally I can use C2 for the former and something like constraint solvers for the latter. See:

https://github.com/lynaghk/cassowary-cljs-demo/blob/master/s...

Getting everything tided up for public release was actually on my agenda for this weekend, but someone found the github and posted to HN early =P