Design for the target device, not your computer.
What browser are you testing with on your device ? Chrome for Android will likely give the best HTML5 performances on Android.
What is the OS of your device ? What is the hardware/model of the device ? Is it recent enough to support HTML5 ?
Have you tried playing with the project settings like "Downscaling" and "Sampling" ?
Have you followed the performance and memory usage tips ?
Phone: Desire S
Android Version: 2.3.5
Memory: 768 MB
Program used: Intel XDX - Android without crosswalk
Used settings:
I tried also with GenyMotion (Android emulator) and looks just as bad.
If anyone cares to spent the .apk of my game.