Snake has 3 stages:
1st - When you first see it, it will do normal attack on turn 1, nothing you can do here, just hope it doesn't crit. Then on turn 2 it will do skill that you MUST interrupt, after you blocked it, it will swallow you.
2nd - In stomach snake will use 2 skills, first is some shaky move that only does 200-500 to all, this can be ignored unless you have another interrupt ready for next move. Second move it will use is some acid stuff like Hanzo, this will hit few thousand, it's another MUST interrupt, after that it will * you out.
3rd - Here you are back vs snake, it will have about 2k~ health left, it will do one normal attack and if it doesn't kill anyone, you win. If it does, it has bloodthirsty so bye bye.
Idk how the guy above did it, he seems to be short one interrupt, i guess he healed before acid so it doesn't one shot him then healed after to counter the damage and get rid of poison. I would recommend Guy/Kimimaro and Cow Zabuza or Neji with main specced for max heals instead and block the skills.