We simply don't have enough batting class. Amla is a rock of late and Faf is good for a score most days. But the rest are inconsistent and exposed by movement....starting with Miller and de Kock, who as veterans should be coming through for the team.
AB may not be the player of 5 years ago, but he is still a giant by comparison. Get him to agree a limited stint through the WC....he has a long time to be retired.