The issue is that there is not enough of the generally playable one mana options for one person, let alone two people in the colour, not that there are not enough total to have black fully covered for its potential needs in the discard department
Diminished Returner is a Creature phyrexian skeleton card in Magic: the Gathering MTG
Yes, there is a limit in place for mana value 3 or less, but if youre already caring a lot about your mana curve and the amount of mana you spend on spells, chances are you will have plenty of targets for this card
Far and away the most popular use for Dramatic Reversal is being loaded into an Isochron ScepterIsochron Scepter: That combo's in more than 90,000 decks according to Commander Spellbook
Hero of Goma Fada: a late cast that is Standard-only
Loxi: Ironically, I think most people will play this for the Cyclonic Rift part of the second bit and just use this as great mill/discard-fodder