We are experimenting in de-coupling with pretty encouraging results at http://theinformr.com.

First we migrated our legacy app's front-end route by route from Symfony to Symfony2 + JS and are iteratively migrating parts of the backend to WP with help of the REST API.

The motivation is that WordPress + ACF is just works. It gets content into the db where we need it without re-inveting the wheel.

WordPress is familiar to most anyone we onboard and we free more time for our devs for front-end work which Emily points out as an advantage in her article.