While it's kind of a toned-down version of pervious Ulamogs - ward is not indestructibility and exiling half a library is not the same as exiling 20 cards per attack - it's safe to assume you'll at least hit a four-drop, making the Defiler an 11/11, and giving it annihilator 4
Many effects like this have restrictions
EX1-015 U Digimon Lv.4 Garurumon Color Blue Cost 5 DP 5000 Digivolve Cost 1 Blue 2 from Lv.3 Form Champion Attribute Vaccine Type Beast Card Text 2 [Inherited Effect] [When Attacking][Once Per Turn] You may play 1 [Matt Ishida] with a play cost of 3 or less from your hand without paying its memory cost
Key Features Sporting a reimagined design, Pokmon Trading Card Game Classic contains everything Trainers need to play and collect, including: Three Preconstructed Decks: Iconic cards from the history of the Pokmon TCG, including Base Set Venusaur, Charizard and Blastoise, headline three specially constructed 60-card decks featuring Grass, Fire and Water Energy types
It simply makes the game hurt
In decks like Lazav, the Multifarious, those cards in the graveyard are still very much an asset
