You are completely missing the point of directives. Your proposed alternative strategy of using "only jQuery, Underscore templates and a CommonJS compiler" will leave you with DOM manipulation code entangled with your controller logic and a nearly untestable mess. Directives are meant to encapsulate any code that directly deals with manipulating the DOM so that stuff doesn't leak into your model or controller logic.

You of course don't have to throw everything into directives but then you risk making your code less portable and your tests more brittle. Wrapping a jQuery plugin in a directive is so trivial it's not even worth mentioning, and it certainly doesn't result in "enormous amounts of glue code to please AngularJS".

> over-complicated testing procedures

And this is where you showed your hand. You can't have written tests for an angular app because if you had you wouldn't have made such a bizarre statement. Angular's dependency injection combined with the fantastic Karma test runner makes testing an absolute breeze.