Sabbath have had an off-stage rhythm guitarist/keyboardist for years to beef up the sound when Iommi plays a solo. Just listen to the Heaven and Hell at Radio City DVD, the extra guitars can easily be heard there.
Ozzy's voice was really strong at the Mountain View date that Tony, slap and I were at last summer. I recall him only really fucking up Children of the Grave and like one line of War Pigs. Whatever he's been doing for the last year or so for his voice has definitely been working.