Steps to replicate:

1. open the /rest/api/2/field resource on JIRA OnDemand
2. find the Epic Link field schema. The schema is {"type":"array","items":"string","custom":"com.pyxis.greenhopper.jira:gh-epic-link","customId":10600}
3. open /rest/api/2/issue/<issue key> for an issue that has an Epic Link field populated.
4. find the Epic Link field

Result: A string is shown, whereas the schema says that an array should be shown.

Expected result: The epic link field can only ever contain one value, so the schema shouldn't state that it contains an array.