I agree it's better once it's in play, but it's a lot harder to land a 3cc enchantment than a 1cc enchantment. Consider that your opponent plays the following:
Wasteland
Rishadan Port
Thalia
Swords to Plowshares (for Deathrite).

Additionally, you can cascade into Dread of Night.

Goblins will similarly bring Ports and Wastelands, and Merfolk will have the Wastelands and Dazes. Additionally, both of those decks are far from dead when you land the card.

E. Plague is definitely much, much better against Elves. I might consider just running Darkblast if I thought I'd face both Elves and Thalia decks.

Golgari Charm also exists.