Your new AOC file must modify device class hirerachy. Please make sure your did all the steps documented in this IBM Knowledge Base link:
http://www.ibm.com/support/knowledgecenter/SSSHRK_4.2.0/itnm/ip/wip/disco/task/nmip_dsc_editaocfile.html?lang=en
Double check that you did the following steps:
5. If you created a new AOC file, add a new insert to the class.classIds database table in the ClassSchema.cfg configuration file.
6. Edit the startup options for the ncp_class process and set the -read_aocs_from option to ensure that the new or changed AOC files are read.
After the next full discovery you should see you new device classified correctly.