I'm surprised that nobody with actual Multiplayer experience has commented on this.
The multiplayer functionality in Construct 2 is perfect. It's some of the best multiplayer programming you'll find and uses all modern multiplayer coding methods.
The solution to your problems ISN'T in not using Scirra's multiplayer examples as a starting point. Look at them, learn proper input prediction.
Use Construct 2's interpolation
Use subtle extrapolation, through peer states (stored within byte values)
Slow it down, allow the host and peer time to make sure they're synced up before important events
Remember that, because you'll be able to use that to your advantage often.
Run cell checking for player characters. Basically, what I mean by this is divide your layout into 256 evenly sized sections, or cells, and sync the player's current cell position to the host.
Having both values, the host can interpolate (slightly), pulling the player closer to that cell's position. This will make up for some of the positioning latency, even if just a little.
OPTIMIZE! Not just your multiplayer programming, but everything else to. Once one peer suffers from poor performance, so does everyone else.
Round synced positions.