Clearly he did it wrong, there's no strategy that will checkmate somebody on the first turn, so to speak. He should have anticipated the Basi and adapted accordingly, it's easy as it's only one model to work around rather than a whole army. Tip for fighting Stormcast. They're the Statline Army now like Chaos was in 8th, they have the most powerful models bar none by a long shot, I've seen five Stormcast Paladins take on ten Ogre Ironguts with the Ogres getting first attack and the Paladins massacred them. This is balanced out by the fact that the Stormcast have only the most basic synergies. In order to beat Stormcast, make sure you attack them with your entire army working as a whole and keep your synergy high, because if you don't do that and wind up in a straight up fight with few buffs, they'll walk all over you without breaking a sweat. And keep in mind that if your Stormcast opponent is a smart player, they will base strategy around preventing you from synergising and will try to force you to fight on their terms rather than on your own, so really try to control the battlefield as much as possible to prevent this from happening.