This is clearly a fixed version / apology for
Delver of Secrets, in addition to the clear
continuation of storyline. The follow-up element
of the card is neat, but the fix will no doubt
be too late for at least some of the people who
have been smacked around by Delver decks in
various formats! Though it doesn't quite have
the same take-over-the-match nature as its
predecessor, I actually think it's still good
enough to at least consider, though perhaps not
in formats where Delver is still legal. You're
certainly likely to have mana to protect or
disrupt at the time you can cast it on curve,
and there are almost as many reasons to want
spells in your graveyard as in your hand.
Flashback may not be coming back in this block,
but certainly things like Spellheart Chimera
won't mind being in the same deck as this card.