The Garden Spire is a realtivley quick match. Getting there is the hardest part. Pilot your sparrow to the marked location and get ready to fight some of the biggest guys in the game, The Cabal. These guys go down pretty fast if you aim for the head. The sheilded enemies need to be shot in the arm first. Then they will drop their sheilds and be open for a headshot. You don't even have to clear them out since it isn't an instanced fight. Just get to the console and deploy ghost and you win the mission.