Domain Mapping is slowest loading plugin on many sites?

I'm trying to optimize my server (see my other recent post) and so I installed the P3 plugin to analyze what's slowing my site down:

On sites that are running WooCommerce, that's easily the biggest one and I'll take that up with WooThemes.

However, on sites that are not running WC, Domain Mapping is easily the slowest loading plugin, with 33 or 34% of the site's total load time. That's a pretty significant chunk. Are there ways I can optimize how it runs? Are there any planned speed optimization updates in the works?