It seems that in 6.3.3 are new OID for CPU/MEM usage.
ghost n9000 # snmpbulkwalk -c XXXXX -v 2c -t 10 -r 3 XXXXX system SNMPv2-MIB::sysDescr.0 = STRING: Cisco IOS XR Software (Cisco ASR9K Series), Version 6.3.3[Default]Copyright (c) 2018 by Cisco S...