Maybe tuning down a half step would have helped, Brian is at the end of his range on most songs and sounds flat (though his bad hearing might be an additional factor). He served well and long for AC/DC - and their huge mass appeal was built on his vocal chords, never mind the Bon Scott myth. AC/DC only became a household item (and left the rock fans gated community) with Back in Black and that was his voice. He screamed over the Young riffs in A and E for 35 years, I hope he can enjoy his health and the remainders of his hearing for a long time still.
Brian is 68, Axl is 54 - that is a difference in vocal years, especially with the type of strains their vocals took. While the Axl haters have a point with his prima donna'ness and his tendency for off-(key-)nights compared to the ever-consistent Brian, there is no denying that Axl's voice still has more agility and will be less ultimate-range-tested on that AC/DC tour than Brian's obviously was. I also have a hunch that Axl's singing voice is less removed from his talking voice than Brian's is (who had to limit his work with AC/DC to, say, the upper quarter of his natural range). Whether Axl will still be able to sing like Brian did until recently in 14 years from now is another question though. His hearing though will probably be better - he is fortunate enough to have more gigs with in-ear monitoring already under his belt, call it the grace of later birth: Axl only began walking the stage when lead singers in hard rock bands could hear themselves properly, either with late 80ies state of the art conventional monitoring or those ear plugs.
