This Enchantment costs 2WW (2 colorless, 2 White) to cast and makes all creatures into vanilla 1/1 creatures. Making creatures lose all abilities is especially important, as many creatures in Legacy have powerful abilities. Nerfing creature abilities and making them into like 1/1's is one of the most powerful control strategies in the history of Magic. However, over the years, playing a 4-drop Enchantment has become harder and harder as the format has sped up. Also a card like Humility does nothing against a lot of popular combo strategies that exist in the game today. Resource deprivation decks such as Stax have out-moded decks that would use cards like Humlity.
All that being said, Humility doesn't see a bunch of Magic Online play any more. However, one of its best friends in the lock-down deck, Grindstone, is also being reprinted in Tempest Remastered at mythic rare, as well. These two key cards seeing greater supply on Magic Online may bring interest back to that nasty Icy Manipulator/Winter Orb deck, even if not back into any meaningful competition. At the very least, there will be a dip in value for old Tempest copies of Humility. If this is a card you've considered picking up online, May 2015 will be a good time to watch for it as many people will be selling copies to fund their Tempest Remastered drafts.