With just 4 NICs your options are very limited in regards of separating traffic but providing the required redundancy. IMO, for hosts with iSCSI networking you should have a minimum of six NICs. Two for Management/vMotion, two for iSCSI and 2 for VM traffic.
Without any knowledge about the host's workload (i.e. number of VMs and their resource requirements), it's nearly impossible to recommend a configuration. What I wouldn't do though, is to break redundancy for the storage/iSCSI network.
André