Does a Hyper-V cluster need its own VLAN?

The hosts don't necessarily need to be completely isolated from every other VLAN. You can use a shared server VLAN, but separating host management from VM traffic gives you a clearer security boundary. Allow the management access the hosts need through the firewall rather than assuming they only need to reach each other.

For cluster communication and live migration, a separate network is worth considering. Those host-to-host paths don't necessarily need to be routed, and keeping them apart from ordinary server traffic can make troubleshooting easier. Configure the cluster networks according to their intended roles rather than assuming that creating a VLAN alone directs traffic onto it.

Since storage is already separate, the next question is how much isolation you want for the hosts themselves. Sharing the server VLAN is simpler, but VM traffic and host management then share that network boundary. A dedicated management VLAN gives you more control over who can reach the hosts.

For a small cluster, a direct host-to-host link using dedicated adapters is another option for private cluster traffic. It avoids a switch on that path, but you still need IP addressing and cluster network configuration. Don't assume every kind of cluster or migration traffic will automatically use the link.