While it isnt as resilient as Prismatic Omen or Chromatic Lantern, being a creature has its own benefits, like being more easily recurred and a blocker or attacker
With the ability to create a swarm of little nippers, then pump them up each time he attacks, Edgar naturally works best in a horde-style deck that can swiftly overwhelm opponents
Lots of legendary equipment grant ways to evade or trample through your opponents, so Kassandra could be a fairly interesting go-wide commander
Then again, one of the allures of the format is its inherent unfairness, so I guess it's mostly that I kinda feel playing more than four copies of a card - in particular in small decks - could break randomness and replayability of a format
They dont seem too overpowered at first glance, and they bring some interesting new interactions to the game
A Counterspell with Buyback