AOE Balance will always take priority in terms of cards. After that, you can use your AOE Spear/Arrow. I always try to ask my co-AST if they want to Balance first if we’re both holding them. If they don’t answer, I wait about 5 seconds into the pull, and if they haven’t used their card yet, I do mine (of course, half the time they still overwrite it after I asked and waited for them to use it first).

I got into the habit of making macros with sound effects whenever I was readying a spread Balance/Spear/Arrow. Just something like “AOE Balance HELD and READY! Using in 5! <se.3>”. It was...semi-effective. Usually, you just have to pay really close attention. However, I will not hesitate to call out an AST that overwrites my AOE Balance with something stupid, like an AOE Ewer or Spire (though I usually don’t have to because sometimes party members will say “RIP Balance” for me lol).