Yes, both NetScaler VPX or MPX appliances support High Availability (HA) configurations.
NetScaler VPX and MPX servers are not redundant, unless configured in HA mode with a partner. As part of your back up and recovery strategy, it is highly recommended to deploy an HA environment when using NetScaler VPX or MPX appliances.
It is also important to provide redundancy for other hardware and software components. For example, power supplies and local disk drives may not have redundancy. A failure in these components may result in data loss.