The unanswerable question about Vaughn is whether he would be hitting better if he had been getting more consistent ABs all along.
There’s no question that Yelich has been horrible for some time now and there is certainly a rational argument that the offense would have been better off if he had gotten more ABs as DH than Yelich, even against RHP.
When someone says that Yelich should be moved down in the order, that seems to support that argument. Vaughn’ seems better suited to batting sixth or seventh than Yelich in his current state.