Board Thread:Questions and Answers/@comment-112.198.29.122-20141203202002/@comment-5007614-20141204164033

Order of activation matters, so the first two characters' SBB would not benefit from the added elemental attack buff of the 3rd character.

Unrelated to elemental buffs, but order of activation is important because similar buffs will replace others. For example, Duel-SGX adds 60% crit rate to the party, while Creator Maxwell only adds 30%. If SGX activated its SBB first, followed by Maxwell, the party will only benefit from +30%.

Please note that in some very rare cases, some units' BB/SBB do not apply their effect until the very end of their animation, as opposed to immediately when activated. Those units do not come to my mind at the moment, but they are rare and few.