The most useful were onoki and tsunade for obvious reasons.
Then gaara and mei - gaara saved mei and his sand defences proved useful. Mei is very underrated here - she blocked that giant katon which needed like 10 other people to block it when madara used it for the first time and her water dragon was also used as a base for other techniques. Her hidden mist jutsu was needed for that combination attack.
A was the least usefull. He needed help from onoki to break through susanoo, something tsunade did alone.