From my observations, you should typically gather about seven strong allies and engage on the closest terrain suitable for your tactics. The healers should stay arrears.

[The prompt response comes from the fur and leather geared warrior with a massive axe strapped to his back. He's walking by on his way through the coven's courtyard. He can be stopped for further elaboration, probably.]

...And keep your spear bearers away from cliffs.

[They have a frightening tendency, for dragoons, to backflip off the side of the arena.]