Multipath issues with iSCSI storage

Setup:
- 1 RHEV-M (i7, 8 GB RAM, 2 x GBit NIC)
- 2 Hypervisors (Conroe, 8 core, 24 GB RAM, 6 x Gbit NIC)
- Infortrend iSCSI storage 4 TB (4 disks),  4 x Gbit iSCSI channel
- Cisco Gbit switch (does no trunking according 802.3ad (at least our network guys did not succeed in configuring it....))
- Since switch doesn't support trunking we drive four subnets, one for each iSCSI channel.
- Each channel has a 1 TB LUN configured.

Problem:
When we configure a storage domain and add all 4 LUNS to the same (master) storage domain, the second hypervisor (not SPM) looses connection to storage domain after 5 minutes. (Could not connect to storage domain attched to it)
I see strange multipath errors on the hypervisor console.
This behavior is reproducible (did a fresh setup for reproduction).
It is not related to network config issues, afaik, we defined 4 logical storage networks in the cluster.
I can manually connect to the LUNs from each hypervisor. (iscsiadm)

- Solution:
Configuring the 4 LUNs in 4 seperate domains works fine and the second hypervisor doesn't loose connection.

- Question:
It would be nice to see our 4 TB  storage in one domain instead of 4 domains holding 1 TB each.
Did I miss something with configuring storage domains properly or is this issue known ?