Rasmus,
have you looked at the various channel bundling options, esp. 802.3ad? That should give you load balancing across two or more active/active links, if your switch supports this. You'd then have a single bond0 interface with a single IP and since you use two client machines, the connections should be assigned to different network interfaces.
Using IPs from the same subnet for multiple interfaces of the DSS does enable load balancing for incoming traffic only - all traffic from DSS to the server will most probably use the interface with the default route. So if you have only high write traffic, but fairly low read traffic to/from the iSCSI devices, you'd be fine. (Just kidding - that should be an extremely rare case

)
With regards,
Jens