I disagree.
In my experience, Dread Return as a one-of boasts a marginally negligible drawback in first games and serves as a perfectly reasonable win condition in the event your Ichorids are exiled. You can't always solely rely on them to win games, which is where Narcomoeba in conjunction with Cabal Therapy and Bridge from Below becomes your secondary line of play. What you're doing is generating advantage by creating tokens, which is facilitated faster with a triple-sacrifice outlet built into one card - in addition to giving you
another monster.
Utility aside, playing one in the main is entirely acceptable. As for being a "win more" card: I just disagree with that term all together. You're going to at times have lots of dead cards in your hand over the course of a game with Dredge (i.e. Narcomoeba, Bridge from Below) - which all sooner or later find their way into your graveyard. Dredge - especially in the first game - can't always rely on Ichorids to win games. Dread Return will generate a huge board advantage with multiple Bridges, in addition to bringing back a potentially game-ending creature.
Seriously, I've seen lines of play where you only hit a single Narcomoeba with three Bridges, flashback a Therapy knocking out some removal like a Swords or something to that effect and follow it up with a Dread Return. The deck deploys a strategy of mowing through itself like a buzz-saw, so I highly doubt you can justify playing a
single a card as effective in this archetype like Dread Return as being "win more" when it obviously is one of the most powerful spells in the entire deck - main or side - at a reasonable quantity.
Also, how do you figure you need a second Dread Return and a dedicated target to win you the game? You just run out a single
Flame-kin Zealot and that will generally do it in one shot.