DiscountApplicationStrategy.All has worked for me as of the April release. Below is a snippet of my return code if it helps.
return {
discounts: [
{
targets: targets0, // Apply the discount to the collected targets
value: {percentage: {value: discount0}} // Define a percentage-based discount
},
{
targets: targets1,
value: {percentage: {value: discount1}}
},
],
discountApplicationStrategy: DiscountApplicationStrategy.All
};