I'm just with the same problem on iOS. Multiplayer games I'm working on runs smoothly on Android but on iOS is another history.
I'm only been able to make it working on iOS using Bowser, exporting the games to HTML5. Bowser is the only browser on iOS that, to date, supports WebRTC. But Bowser has his pitfalls, is not as competent as Safary or Chrome in terms of funcionallity. But to make Construct 2 multiplayer-games work on iOS is near perfect.
I'm trying to use CocoonJS also. But all my tests have failed and I think that CocoonJS doesn't support WebRTC at all, or his support is not as complete as to make multiplayer-games made with Construct 2 works.
A question: could it be possible to modify the Construct 2 Multiplayer plugin to use that Cordova/PhoneGap plugin for WebRTC jayderyu just mentioned?