While doing the installation of OEM GC 11.1 on AIX 6.1, I noticed that there was no automatic discovery of the Middleware targets.
This is due to bug 9969664.
The solution provided in MOS Note:
Error when discovering and monitoring secured weblogic domains on AIX platforms (using t3s/iiops protocols) in EMGC11.1 (Doc ID 1208874.1)
did the trick for me and discovered the 8 additional Middleware targets.