Currently, my custom animation class's
ax_line1, = ax.plot(...)
self._drawn_artists = [ax_line1, ax_line2]
If you want to set the data in parallel, I think your best option is to just create all of the line objects that you will need by calling the constructor that many times. Then you can iterate through them and set data as appropriate. If a lot of your lines are supposed to be identical share attributes, you can achieve this with the update_from method of matplotlib artists. You could freeze some of the line objects to allow them to be copied, but then you wouldn't be able to change the data.
That said, when you consider that you'll be needing to undraw lines as well, I'm not sure how much time this will save you. If you have a massive amount of data that you can handle in a very parallel manner, then it might be worth it.
Still, if you really want to speed this up, you should probably use blitting. The basic idea behind blitting is this:
FuncAnimationfunction handles the rest with shocking efficiency.
Because all of your operations involve updating lines, this is a pretty ideal scenario in which to use blitting. Matplotlib's documentation on blitting is not incredibly clear, so, if you want more detail, I wrote this tutorial, which has example code and such.