This is overcosted, even in block. Cephalid Pathmage is a better choice in block for this ability and it came out in the block after this one. Sure, in block, it was the only card that made something else unblockable, but was it worth it? Not really. As I mentioned before, cards like Cephalid Pathmage or Crafty Pathmage are better than this. Why? First, they're on creatures, so they stick around for a bit and don't require the mana investment right away. Second, they're cheaper than this at 3 mana each. Finally, cards like Crafty Pathmage can be used repeatedly for no mana (the Cephalid has to die unfortunately). Nowadays, the young whippersnapper Standard players have cards like Artful Dodge and Ghostform, so that makes this card really overcosted (although I don't know why people prefer Artful Dodge to Ghostform...). You might be thinking "well, back then it was reasonable to pay 4 to make something unblockable and draw a card". Shadow Rift did better (since it can either be unblockable or it can be used to block that pesky shadow creature your opponent might have) and draws a card for 1.
Pros: Draws a card and makes something unblockable, art is nice
Cons: Overcosted for both abilities, older and newer cards are better at what it tries to do