Slight expansion on the original question:
I have a VM running an ISCSI storage server (TGTD) and this works well disks can be added and made available to other servers
I have three other VM's. 2 for a Oracle RAC installation (12c) and 1 for a standalone ASM installation. Both can see the ISCSI disks and can mount the devices under /dev.
Here is the problem. The device persistence (very necessary) is based on UDEV and therefore the ISCSI id returned by sci_id is key. This can be obtained from /dev/block/<device> normally but this does not operate making the UDEV solution fail and therefore Oracle ASM does not work as the disk mount points can change around following a reboot.
Fusion is a great way to test build concepts and learn so I have used it a lot over the years. Unless I can find a solution to the problem I will either have to move to the cloud (yet more complication) or simply be unable to build complex solutions. ESXi does this with no issues but I can't quite stretch to that for my personal use.