Well, there isn't any level set in stone (minus the 250 level requirement to do the quest)
BUT if you want to erase mana shield out of the equation completely, and hunt comfortably, I would say level 900.
At level 900 you have 5,145 total HP. You have the equivalent to a level 340~ish elite knight. You're not full boxing or standing directly next to the EK, you do have a the risk of a monster leaving the EK if he fails to res, but your exura vita will outheal whatever that monster hits. As long as you're persistent with your healing, you should be completely fine. HOWEVER, you can still get wrecked, so don't get overconfident, still take high caution as these monsters still do a ton of damage.
I'm going to take a stab and say you were talking about team hunts,
I hope I answered your question and gave you somewhat of an idea.
Cheers,
Jay!