Troubleshooting vCenter and ESXi hosts means analyzing different performance monitors, alerts, alarms, and log files. Most analysis can be performed with the vSphere Web Client, but sometimes you need direct access to ESXi or vCenter in order to collect logs or other specific information.
Objective 7.1 for VCP65-DCV and VCP6-DCV are very similar just because there weren't big changes in the troubleshooting approach from vSphere 6.0 to vSphere 6.5. Just the first part of VCSA is new.
The vSphere 6.5 Troubleshooting guide contains in-depth information and examples, and can be found here: https://docs.vmware.com/en/VMware-vSphere/6.5/vsphere-esxi-vcenter-server-651-troubleshooting-guide.pdf.
