Being a black artifact also helps in those decks, so there are lots of little bumps that get this over your standard edict
The actual dredge action is a replacement effect that mills cards from your library
And, while it'll most likely produce an absurd quantity of cards drawn, it's worth considering to what extent we'll be able to use all of those cards, if our resources have to be invested in defending this Leviathan from continuous removal attempts
More than 30 Trainer cards
I am not a huge fan of the Bloodbraid, in singleton formats it is really rather random and works very poorly with certain cards, let alone less efficiently in a lower average casting cost format
That steady stream of free bodies overwhelms slower opponents and forces constant answers, especially in Commander or long midrange games