There are cases where Aspected Benefic from Doublecast is worth using over Doublecast Gravity in Frontlines. It's just really dependent on the AST to be able to determine whether the situation calls for it or not. Similar to how Holy works in PvE as a CC, binding an enemy has a lot of advantage as well due to jobs having a range on their skills. Sometimes though, you might want a spot heal instead if you think the heal can be worth saving someone. It's ultimately dependent on how the fight progresses. In CC, usually damage is better because everyone's damage is at 100% and the number of players is equal, unless that extra aspected benefic can guarantee someone living through a mechanic (ex: blocking enough damage to prevent NIN LB from activating, ensuring someone stays alive long enough to recuperate and get out, ensuring someone has enough HP to get their LB out, etc.). In Frontlines, it depends on a lot of variables: distance, number of enemies, location, target's role, objective, etc.

Having decision-making with Double cast and choices is more of a player's expression on how they want to tackle the situation to decide whether Doublecast is worth Aspected Benefic, Malefic, or Gravity. It's why I like PvP AST a lot; it's such a simple mechanic and skillset, but it has answers to a lot of different situations due to this flexibility.