And our targetting by click strats might be different. I try to poison the back row first?
It might actually be better to not keep the bombers all the way at the back and swap their places with the single-targetters, since bombers' single-target damage is IIRC weaker, so unless the final enemies are positioned good, bombs aren't the best at cleaning up?
EDIT: Just a hypothesis since I don't feel like testing.