I couldn't get it working with a newer SAS 6E card in my 720. Found a good price on a SAS 5/E, put it in a PCI slot and it worked just fine. Bottom line is that I believe you need a card that doesn't do RAID.
Also - in openmanage, that SAS 5/E shows up, but the ports/connectors don't show up in there. But diskpart / disk manager saw them just fine. do you have a single enclosure (1 drive eSATA) you could try just to see if it is the LaCie or the card/fan-out cable?