First thing to remember is to play as team. And try to figure out what a good team would look like and try to get that together.
AB teams with random invites are less powerfull than well build teams.
Your team needs a leader that knows the battlefield and the rest follows blind. The leader should be able to determine what is the best shrine to cap, while avoiding other players as much as possible (both own and enemies).
Then the leader should be able to determine other (alliance) team strategies.
There are certain patterns that indicate how well a team is lead and what capturing tactic is used.
The leader can adjust his/her team tactic to the general tactic.
And this is where things as 'smart mobbing' step in, where teams create advantage by their position and movement on the playing field.
This requires at least two team leaders that know how to play the game and that adjust their playing style.
It is a very solid way to win on maps except perhaps the Lands and Canyon maps.