I don't know much about Magura clutch set-ups. But, have you checked/cleaned the line, slave cylinder, andmaster cylinder? Checked the lever for binding? Is it adjusted properly with the clutch? I believe you can buy different diameter master cylinders from magura. Not many run magura set ups here, you may have to call Magura.
Don't know if it'll help, but here is a setup video from RMATV.