The Multi Sites plugin currently works fine, but does not follow Piwik plugin conventions. It does not expose an API class and uses other APIs when it could access data directly from Archive types. Refactoring the plugin will speed it up, clarify the code and allow it to be tested.
(In ) Fixes #2810. Refactored MultiSites plugin:
(In ) Refs #2810, bug in last commit.
(In ) Fixes #2600