Hi,
I do have a similar problem - try to check - I found out too late mine was a USB 1.1 revision 😢
http://global.focusrite.com/answerbase/are-focusrite-products-compatible-with-el -capitan
Saffire 6 USB 2.0
Works with El Capitan? YES
Saffire 6 USB 1.1
Works with El Capitan? NO - INFO TO FOLLOW
Points of note : If you are using the USB 2.0 version of the Saffire 6, no driver is required. Simply plug and play. If you are unsure whether your unit is the USB 1.1 or 2.0 version please check the serial number shown on the bottom of the device. If the serial number starts 'S2' it's a Saffire 6 USB 2.0, if it starts 'SU', it's a Saffire 6 USB 1.1.
I'll try to get hold on Focusrite to see, if they'll support the USB 1.1 box or not
Kind regards
Peter