Hypnotic Specter? Not exactly!
So lets dare to compare:
1) This ‘mills’ , Hypnotic Specter discards.
Advantage: Hypnotic Specter
2) Nightveil is a hybrid card and thus has the potential to fit in more decks.
Advantage: Nightveil Specter
3) This new guy has an extra point of toughness making it extra relevant versus those who would try to simply Pillar of Flame away the little guys.
Advantage: Nightveil Specter
4) You might not be able to cast the cards you ‘mill/exile’ unless they are lands. Hyppie doesn’t allow you to play what you make them discard anyhow.
Advantage: Nightveil Specter
Winner: Nightveil Specter ?
Now the reason this is not a clear cut winner is because Hypnotic Specter affects things more directly in its random discard than this ever will. It’s also better or at least was better in Legacy.
The comparison is a tad unfair as Hypnotic Specter is not even a Standard Legal card at the time being. For a comparable cost, it would have to battle it out with Vampire Nighthawk ( a card that is more relevant with what’s on the board)
.In its defense though, the Standard format as of late is increasingly multicolored (Dual lands will do that) so its ability to cast the exiled card might become more relevant. It’s also a nice target with the Cipher mechanic (shocking eh?) as you can double-up on its combat damage trigger.