Ok so the Dark archon tech Maelstrom is really good but when you combine it with conclave fleet it is completely nuts. All you have to do is research maelstrom and build a dark archon on your conclave fleet and you can cancel a mobilize to any of your bases. I used this in a game last night to hold the points I needed to win the game.

Maelstrom is by far the best reason to get dark archons.