RotE: Reva mission can't be done once per phase anymore

You've never been able to do the mission after you lost. It is a once per TB mission.

my guildmates and I were able to. Probably was a bug that was never fixed until now lol

Our guild has been spreading that zone over 2 days for at least a year, and not once have I ever seen what you are claiming. 

If you don't star the planet, you have a second day to do the mission.  A lot of guilds are doing that for many planets so they can get more stars.  If you don't star it in the first phase it opens, then you can run the missions the second day too.  But, special missions, like Reva can only be done one time per TB by anyone.

So perhaps there is some confusion in that? 

In the past we were able to do the mission twice if you failed on the first day. On the second day it got reset and you could try again. I remember in Geonosis that was not the case, the KAM and Wat missions could only be done once. Probably got patched and I did not notice since it was a while since I failñed the mission.