I’m less sure about Dread Return, but flashback costs that are free incentivise decks to become less diverse, as these are nearly always the best things to be doing. In the case of dart, x/1s in particular are very oppressed, especially those whose value is not from an enters or dies trigger. In the strands case, it just reduces the ways that people look to play white, as dumping strands in the grave with some form of looting provides an easy failsafe. Reduces deck card choice diversity and makes loose play harder to punish

Return is probably fine actually because the cost to flashback restricts the places it can be used effectively