I'm trying to get all posts by ID's using WP REST API. As per the documentation, we can use filter to use WP Query arguments. Using this with posts end point returns all the posts.
http://demo.wp-api.org/wp-json/wp/v2/posts/?filter[posts__in]=470,469
With V2 This is working for me, more butter then adding custom code
http://demo.wp-api.org/wp-json/wp/v2/posts?include[]=470&include[]=469