I know the OP's example is using DQL and the query builder, but I stumbled upon this looking for how to do it from a controller or outside of the repository class, so maybe this will help others.
You can also do a WHERE IN
from the controller this way:
// Symfony example
$ids = [1, 2, 3, 4];
$repo = $this->getDoctrine()->getRepository('AppBundle:RepoName');
$result = $repo->findBy([
'id' => $ids
]);