What is the complete list of expected JSON responses for DS.RESTAdapter?
Instead of stabbing in the dark, have a look at rest-adapter-test
For example, to fill in your question on response data for bulk updates, L738 describes the expected response data:
ajaxHash.success({ people: [
{ id: 1, name: "Brohuda Brokatz" },
{ id: 2, name: "Brocarl Brolerche" }
]});