I think Sigma has finally got it right with their new Art series lenses. I am saving up for 35mm 1.4 and can't wait to get my hands on it. Does your camera have MFA feature?. I thought only the 50mm 1.4 have FF/BF issues not the 30mm 1.4 DC.
My camera doesn't have MFA, but my 30mm doesn't have consistent FF or BF, it just often completely misfocuses when using autofocus. Sometimes it's fine, and sometimes it's not even close (but the camera thinks it has good focus) so MFA wouldn't help.