Asset compilation slow for EmberJS

We're in the process of transitioning our front-end to EmberJS and plan to use the Ember CLI which should solve the problem we are currently having. Until that time we have multiple Ember JS applications in our Rails app. Running rake assets:precompile locally executes in less than a minute however asset compilation when deploying to Heroku is extremely slow (> 15 minutes) despite the use of PX dynos for deployment.

Here's our build log: http://ift.tt/1brhAXL

Note the compile times of approximately 4 minutes per EmberJS app.

• application_ember_orders => 2015-03-24T21:54


• application_ember_search => 2015-03-24T21:58


• application_ember_search_chrome => 2015-03-24T22:02

Has anyone experienced this problem with EmberJS and the Rails asset pipeline? If so do you have any suggestions about why compilation is so sluggish?