If you have MS SQL Server Enterprise you can enable partitioning and then you don't need to defragment tables other than the following tables in this list (run this as a daily job off hours):
For USM performance these tables in particular need to be defragmented:
ALTER INDEX ALL ON CM_COMPUTER_SYSTEM REBUILD;
ALTER INDEX ALL ON CM_DEVICE REBUILD;
ALTER INDEX ALL ON CM_COMPUTER_SYSTEM_ATTR REBUILD;
ALTER INDEX ALL ON CM_DEVICE_ATTRIBUTE REBUILD;
ALTER INDEX ALL ON CM_CONFIGURATION_ITEM REBUILD;
ALTER INDEX ALL ON CM_CONFIGURATION_ITEM_METRIC REBUILD;
ALTER INDEX ALL ON CM_CONFIGURATION_ITEM_DEFINITION REBUILD;
ALTER INDEX ALL ON CM_CONFIGURATION_ITEM_METRIC_DEFINITION REBUILD;
ALTER INDEX ALL ON CM_NIMBUS_ROBOT REBUILD;
ALTER INDEX ALL ON CM_DEVICE REBUILD;
ALTER INDEX ALL ON CM_COMPUTER_SYSTEM_ORIGIN REBUILD;
ALTER INDEX ALL ON CM_CONFIGURATION_ITEM_ATTRIBUTE REBUILD;
ALTER INDEX ALL ON CM_RELATIONSHIP_CI_CI REBUILD;
ALTER INDEX ALL ON CM_RELATIONSHIP_CI_CS REBUILD;
ALTER INDEX ALL ON CM_RELATIONSHIP_CS_CI REBUILD;
ALTER INDEX ALL ON CM_DISCOVERY_NETWORK REBUILD;
ALTER INDEX ALL ON S_QOS_DATA REBUILD;
ALTER INDEX ALL ON NAS_TRANSACTION_SUMMARY REBUILD;
ALTER INDEX ALL ON NAS_ALARMS REBUILD;