Ashley answered with this:
"Your example loads within a second even in r109. So I guess your computer might be a lot slower than mine...
I've tried to improve the performance of the startup time. In the attached fix.zip try extracting eveng.js over the one in <install path>\exporters\html5\eveng.js. Does that help improve it?"
I had reinstaled 108, but then I got it back to 109 to test your fix, and the game was loading fast again without the fix. Not sure why :/