Sorry, but gear is and always will be a requirement.

There is absolutely no skill level a player can attain that will cause them not to die to tumult/jumps when they have less HP then the damage it deals.

And as for the people who leave? I don't blame them at all. If you know your healers aren't going to survive the phase 5 tumult there's no reason to continue. You've already lost. Any other action is simply an exercise of futility.