From someone who finished it... (Destiny)

by Chappy, Arlington, VA., Sunday, September 25, 2016, 19:05 (3073 days ago) @ Blackt1g3r

The very last part of the raid is a bit of a gear-check. Even the minions will have red level indicators if you're not 370. That doesn't make it impossible; just more difficult. My blind group was able to get up to the last fight on Friday while we were all between 357 and 369 (except for one person who was 374). Once we figured out the mechanics of the last encounter, we realized that we wanted to be a bit stronger, both for survivability and damage. We finished it Saturday with 3 people over 370 and 3 people over 365.

I'd say that 370 or above will make the last encounter noticeably easier, but it can be done as low as 365 - especially if you have some 370s filling out your fireteam. Everything else will be easier over 365, but it can be done as low as 355. Also note that more than any other raid, the last encounter requires that everyone have a microphone.