It is completely viable to export via CocoonJS.
I'm making a game, with many moving and animated sprites, 25 physics objects per screen doing 40,000 colission checks a second and animated backgrounds.
And it all works GREAT on Cocoon!
The only thing I haven't done yet is sounds so I have idea how that works yet.
But CocoonJS is still perfectly viable.
How was 1.4.0 perfect? The whole Box2D.Dynamics library didn't work.