Unless you have really precise, tannic, cool area viognier, there's not much point putting it in your fat, sweet McLaren Vale shiraz, according to recent dim fashion. Tight, austere upland riesling makes much more sense: it gives the red fruit more balance and focus, and draws its finish together. So here you had ripe shiraz fermented on the skins of some earlier riesling, and to great advantage. The wine is more Italianate in structure: more austere super-Tuscan in its lithe tight plunge into tannins that make you drool. My favourite black and white since Coriole's shiraz fiano. Check it, Jancis!
