There are many OIDs and MIBs on the Internet to get same information from devices.. i guess because there are many different version of the devices.
In my case, i solved with below OIDs.
OIDs for CPU & Memory
|ALL CPU||Current CPU||Free Memory|
You should divide the “Free System Memory : 482672640” / 1024 bytes to get 471,360 Bytes to be closed the result of SNMP
on CISCO web site, the OID number is 126.96.36.199.4.1.14188.8.131.52.3.
If you do not insert 0 to end of the OID, you will get “No Such Instance” Message.
there are two MIBs, CISCO-LWAPP-SYS-MIB & AIRESPACE-SWITCHING-MIB.
The OIDs i wrote are from AIRESPACE-SWITCHING-MIB and the OIDs on the Internet are usually from CISCO-LWAPP-SYS-MIB.
I searched what AIRESPACE is, and it was a vendor that CISCO merged in 2005.
I guess at least, by Ver.184.108.40.206 in WLC OS would associate with AIRESPACE-SWITCHING-MIB. and this MIB might not support the number of associated AP and client.
I strongly recommend you to upgrade OS.