Back when people were playing Innistrad/Dark Ascension Limited, mill was definitely a workable strategy in draft. The fact that it only requires a single white mana is also very, very important. A predominantly blue mill deck can make this work. This card essentially wins you the game by virtue of the fact that you can simply outlast your opponent by gaining a ton of life and recycling all of your cards. So while this is the worst mythic rare in the set, in the context of a mill deck, it basically says "Win Target Game...very slowly and painfully."
Since then, Archangel's Light has become a part of some EDH decks. Mostly Narset, Enlightened Master (who can cheat it in to play for nothing) and Oloro, Ageless Ascetic who is gaining lots of life already) have gotten the best use out of it. These particular Commanders can take full advantage of both the life-gain and the restocking. But quite a few other decks have played it. It's just that 9 mana sorceries aren't typically what you're going to be running unless they outright win you the game.
Still, if you come across this card in your collection, don't throw it away in disgust. What it does is extremely epic. It's not what you're trying to do in most Constructed formats. But if you ever face a lifegain deck in Commander, you never know if this one is waiting in the wings.