I'm actually having a similar problem. My game is all about physics. (Peggle style)
I've stripped down as much as i could (to my knowledge)
but im still getting bug reports from players having lagg issues on desktop.
(i havent even decided to release it on IOS / android) it would simply not be possible.
However im also interested in various optimization issues.
(i am testing different things at the moment, so i'll be sure to get back if i figure out something)