They'll be adding Prince who has performed in England in recent times, so RSA will have an extra batsman at least.If South Africa didn't have to depend on someone as scratchy as Duminy, they might have won those last two a bit easier. Of course, they could do worse, but as it was, the West Indies just couldn't produce matches where South Africa needed substantially more than just Amla, Kallis and de Villiers to be brilliant. If Duminy was under real pressure to score when he came in to bat, it would almost certainly have been more calamitous.
However, I could see that working against them in the Tests, if the Windies can find a bowler or two.