The network performance with protected mode is still really bad.
This screenshot is of Flash 11.3 but I have the same results with build 11.4.400.231. See also https://bugbase.adobe.com/index.cfm?event=bug&id=3281034.
Flash Player 11.4.400.252 should address this. Please let us know if you continue to experience issues.
We can't reproduce the issue anymore. So this problem seems to be fixed.