Doing some achievements for the balance of power appearance and just found out that the instances aren’t resetting like the SL instances, you can’t redo them on mythic if you failed to get the achievement on a boss the first time.
Never knew even SL dungeons can be reset and done once again. I swear I tried this when doing Tazavesh once, and despite resetting, we were still 1/8 (killed the 1st boss for HM).
On the other hand, here’s what you can do:
Park your toon (where you doing the dungeon) infront of the dungeon (this is important, because if you get the leader on the invited character, it will take your ID instead of your alt’s fresh ID).
Create a group on the toon you didn’t clear the dungeon with
Sign up with the character you’re doing it on
Get back on the fresh alt, inv yourself.
Accept inv on character 1, enter, GG, you are in a new ID.
They mean unlocking another tint of the balance of power appearance, one of those tints needs the legion dungeon hero, which needs to be done on mythic difficulty.
Mythic difficulty Dungeons have a mandatory weekly lockout for every Expansion they’ve been in; only Normal has been spammable & even Heroic used to have a Daily lockout.