In this scenario: 8 Physical Servers running 10 VMs. I am confused as to why we need 5 licenses/hosts? First step is calculate planned number of maximum VMs running on single host at any point of time. If only 2 VMs will run, we just need 1 standard Windows server license. In total we need only 8 licenses. So it doesn't matter whether we split into two clusters are not, we always license based on number of VMs running on single host. The other advantage I can see in single cluster is, we will have lesser number of VMs running in single host during host failures.
(1 standard Windows server 2008 license covers 2 physical processors, and 2 VMs are allowed. Enterprise covers 4 VMs).