Does the iSCSI VMkernel port have just one NIC.? Then there is No Point changing the Path policy, because if the NIC fails it does not have a change path to send I/O's and will make No difference
But if you have two Vmkernel ports like example iSCS1 and iSCS2 with one NIC each. Then the Fixed policy should work good and the path should fail over provided the port binding is done correctly.
The recommended path policy for ESXi 5.0 is Fixed and for 5.1 ESXi is round robin.