How do I find the best location for an AOE ability

Question

I'm making a game in unity3d. I have an AI agent that has a " "targetFinder" method to decide who it will attack. For basic "nearest enemy", it's pretty straightforward:

/* TargetFinder
   Finds the closest enemy */
Transform TargetFinder(Transform source) {
  GameObject[] EnemiesInScene = GetEnemies();
  enemies = enemies.OrderBy(
        (GameObject g) => Vector3.Distance(g.transform.position, source)
    ).ToArray();
  return enemies.Length == 0 ? null : enemies[0].transform;
}

However, let's say I want to give the AI a "fireball" AOE attack, which does damage in a radius and travels from the enemy to a fixed point in the scene. I'd want some sort of method like:

/* TargetFinder
   Finds the transform T within RANGE of SOURCE that maximizes 
   The number of enemy units within RADIUS of T */
Transform TargetFinder(Transform source, float range, float radius) {
  GameObject[] EnemiesInScene = GetEnemies();

  // ???
  return T;
}

Given the enemies, what's the best way to find T? I was imagining a few ideas, but they all seemed very brute-force (e.g. instantiating a bunch of colliders, or doing some sort of topography and picking the highest point)

Would love any insight on if there's any algorithmic or unity-based approach to solving this targeting problem