Okay, so you've milled 7 turn two and have zero board presence. You're probably losing...?
I don't get Mind Sculpt either. If they kept their 7-card hand, they have 53 cards in the library. If the game goes 10 turns (and you'd be lucky to do this without getting overrun), you have to mill 43 cards. Mind Sculpt hits for 7; that's 16% of the life total that your deck is going to hit. Would you play a card that read "1R: Sorcery: Deals 3 damage to target opponent?" (well, 3.25 or something, but you get the idea)
Okay, so you power up Jace's Phantasm. But that card is clearly designed to beat the opponent down; 5/5 in the air is a lot! So are you running a mill deck or a beatdown deck? If you're running a mill deck, is Phantasm just going to be a wall? If you're running a beatdown deck, what does this give you that Delver doesn't?
I'm not trying to be a dick or anything; I'm just struggling to see how Jace's Phantasm is better than Delver. Sure, getting a 5/5 in the air early is enticing. But for once I feel like the "dies to removal" argument is valid. If I lay Phantasm turn 1, then spend resources to mill my opponent and power it up, I effectively get 3-for-1'd when my opponent Doom Blades it. The reason Delver is so good is that you don't spend any resources to transform it, and you can realistically attack for 3 in the air on turn 2. The only thing you give up when it transforms is a tiny bit of information about your hand. Jace's Phantasm requires you to waste time durdling about with milling, while your opponent is building his own board.
If I'm pairing it with Delver, I'm diluting the instant and sorcery pool, thus making Delver worse, or I'm taking a slot away from some other creature. I have a hard time imagining a Delver list that would really want these things.
Maybe I just don't have enough imagination, but I'm really struggling to envision a brew that consistently gets this thing to a 5/5 enough ahead of the curve to make it worth running.
Now, if Jace's Phantasm was a Zombie, we'd be going somewhere! I'm sure Alchemist decks could fit him in.