Disk Queue Length is found within the SNMP informant MIB. The OID for it is 18.104.22.168.4.1.9600.1.1.1.1.7. You can see the branch here:
Keep in mind that you will need to install the SNMP Informant agent on the remote system in order for this to work. You can get it from here:
Is there any better way to monitor disk performance without having to use something like SNMP informant?