Currently you have two options:
  • Always automatically face your target
  • Never automatically face your target

Both of these options are bad.

If you are a healer, automatically turning to face your target can cause wipes when you need to face a certain direction for mechanics, or when an instant heal causes you to suddenly rotate 180 degrees while running out of an attack. The same goes for playing a Summoner who suddenly spins around because they tried to use Rouse/Spur on their pet. There's no reason you should ever need to face your target when doing a heal, because the game doesn't require you to be facing friendly targets to perform friendly actions.

Likewise, you should always turn to face a target when you perform an attack that requires you to face the target. Trying to DPS with auto-facing disabled is a complete nightmare, especially for melee who frequently run through an enemy's hitbox to dodge attacks or to hit positionals.