There are several issues with non-core (angular2.js) bundles we publish to npm:

• we are not using any bundle arithmetic which means that we bundle parts of the core with those optional bundles. This is mostly visible in http where the bundle is pulling most of ng2 (if not all!) and is in fact bigger than ng2 itself (!)
• non-core bundle import non-public APIs (ex.: angular2/src/core/facade/lang in router). This makes it pretty hard impossible (?) to move to CJS bundles that wouldn't have to bundle core again.

cc @jeffbcross @rkirov