Structure Decks available in game (including those not owned)
Trance Archfiend is special in that you can use its effect to discard a Dark World card from your hand, activating its effect
Players can call the summons for aid in battle
You can use Yuna, Hope of Spira, to reanimate them for free with a finality counter, or Rydia, Summoner of Mist to reanimate them by paying their mana cost
in a Commander game, they might just save their removal for a more pressing threat from another opponent
As for Holistic Wisdom, green has a lot of recursion and while being repeatable is nice, having to exile a card from your hand means it doesn't generate card advantage like Eternal Witness and friends