The datasource configuration is the same for both modes.
Difference is that the domain.xml contain more than one profiles (as standalone*.xml does).
You need to check whether you use the correct profile. The server is part of a server-group and this group use a specific configuration profile.
This profile need to have the datasource. Also you need to add the driver as a module (manually) for all instances if you use more than one.
If that did not help you should provide more details.
Did you create corresponding module (com.oracle) on hosts all hosts in domain?