You do realize that Jiraiya almost took out Pain by himself, he figured out the entire whole six paths thing by himself where it took many of the villagers and Jiraiya's message to figure it out. We have never really seen Tsunade fight until now with the most recent fight. I think Jiraiya plus Tsunade or Oro would be enough to take out pain then add the third to take out Konan.
Tsunade would have more than enough strength to destroy Itachi's Sussano. Jiraiya can seal amaterasu so obviously oro and tsunade would be able to as well and oro can just do his usual body exit thing to escape it. Tsukyomi would end up causing a problem but those three are smart enough not look in his eyes so they would only end up getting caught in his regular genjutsu. Kisame wouldn't be a huge issue though he would be the tipping point to make the fight very difficult the sannin.
In short you severly underrating the sannin, we have just the sannin after they got old and sick, they were much more powerful in their prime. Just remember that most of akatski was taken out by people quite a bit weaker than the sannin.