I have however also seen a few installs having VC running in the same VI environment that it is administering, and it's normally working good too, but there are a few situations where you will need to have the VC server running outside this environment (for example when enabling EVC). If you have enough servers in your environment to seperate the VC server in such situations it's not much of a problem. HA runs independently of VC, while DRS and VMotion needs VC to work.
We do it in >90% of our customer deployments. The only thing you should make sure is that you have a license server (possibly an additional/backup one) on a physical server (could be the backup server for example which needs to be physical anyways) otherwise you have a chicken-and-egg problem starting up your VC 😉