As long as the Dark Archon is a lose more card, I don't see how Protoss can function. I don't mean Dark Archon causes Protoss to lose, but that it seems to be a major insult and injury to Zerg and Terran. There is a lot of need for Protoss to go above the Supply cap of 200/200, but it's not proven to be good in other matchups. Lastly, I don't think the Dark Archon can only be used for Maelstrom on Devourers and Zerg drops. Obviously, Dark Archon can keep the drop in place until it dies, but can anyone justify Maelstrom above Reaver for Ultra? Every late game PvZ will probably be high economy.
That lone Dark Archon trying to win the game has never been a reality. Early programmers should have saved its shields.