If you add a dependency on A to B and a dependency on B to C this should work.
See Class Loading in AS7 - JBoss AS 7.0 - Project Documentation Editor for the 2 ways to do this, manifest entry or jboss-deployment-structure.xml.
This is bit different, you need deployment dependencies not just classloader dependencies.
In short, you will need to have JBoss AS7.2+ and add jboss-all.xml that allows you to specify deployment dependencies.
Otherwise there is no order enforcement, as deployment & classloading is concurrent.
What Frank suggests that if you also need to access classes from one deployment to another.
I would recommend to upgrade to WildFly 8.2 or 9 as 7.x stuff is quite old this days....