A problem with this process has been identified in ESXi 6.0 where, for Active/Active arrays, failover is not triggered when other paths to the LUN are available. A fix is being investigated by VMware. This article will be updated when the fix is available.
VMware support said this will be fixed in ESX 6 Update 2, which could arrive at the end of March.
I think this is a CRITICAL bug ans should be fixed ASAP.