Why was iSCSI support deprecated? I recently developed an interest an iSCSI, which makes me curious; not an Isilon user, though.
My guess would be that Isilon/OneFS is designed for file storage, instead of block storage, so having a block storage layer on top (like iSCSI) seems a little ungainly. Instead I expect Dell/EMC would prefer you investigate the VNX platform!
Edit: By "file storage", I'm talking about storage mounted using protocols like SMB and NFS.