Sailor Sakura is pretty manageable as long as you, or a teammate has a way to ignite her every round. Otherwise, yes, she is frustrating to deal with.

Hiruzen is also relatively easy to handle as well, just have someone in your team keep a ninja with a interrupt/control mystery available for when Hiruzen dies and attempts to cast his reaper death seal. Unless the lag monster gets you, which has happened to me, it isn't much of a problem.

Death Possession Blood Hidan is probably the most annoying to deal with. His attack stat is based off of his maximum health, and since he has 300k hp in Rescue the Jinchuriki, his attack is insane and it one shots your ninjas. You want to keep him immobile or defeated; at the very least, stop him from using his mystery and keep clones across from him.

You can ask around your server or group if anyone had done the Jinchuriki event for the day and ask them what teams were in the second wave to prepare. Or, go in with a team to see the second wave and intentionally lose (don't use mysteries or go in with a low bp team), so you can see the teams in the second wave yourself to know how to counter them properly.