After removing agent, you won't able to get metrics on discovered resources and auto-discover a new. vROPs gives you high level about VM. As you mentioned Hyperic agent gives deep info about VM, such as OS (e.g. Windows, Linux, AIX, Solaris), processes, applications and DBs. IMHO you should investigate the reason of high CPU (e.g. a lot of non default monitored metrics, short time interval, a lot of monitored services/processes, check if debug mode is opened).
If you up to now have been worked with hyperic agent it will disadvantage for you to work without.