I've been on chat with Microsoft (re Mail and People apps - they stopped working couple of days ago), and they instructed me to uninstall KB3084036 and then to hide it from being installed again.
While uninstalling an update is easy (Settings -> Update and Security -> Windows Update -> Advanced Options > View your update history > Uninstall Updates), it will only keep installing again. In order to prevent this, Microsoft has issued a troubleshooter package, which may hide updates from being installed. The description and download link are here:
https://support.microsoft.com/en-us/kb/3073930