JBoss 7.x improved the server performance significantly by implementing modular development. Instead of going with OSGi, they implemented their own JBoss modules, a precursor to what should be a JSR 294 (Java modules) compliant implementation. But as it stands now, this is simply a vendor-specific module implementation.
As a result, our agent classes are no longer available in bootclass loader by default. We need to make few changes in JBoss 7.x bootstrap files to make DevTest agent work.