>>542462435
For Cyrene Main DPS?
RMC contributes to a quicker Cyrene ult because Mem contributes Ult stacks without any restrictions and gets future buff. Cyrene's nuke bounce count is determined by how many people on the team have "Future" (Cyrene's mini ult buff. She doesn't count for this but get 1 bounce minimum), so 4 bounces with a normal team, 4+3 bounces with a full memosprite team.
With E1 her nuke in a remembrance team bounces 7+12 times (19x60% = 1140% damage). The issue being that to trigger this attack, she needs to get 3 stacks of "Story". She gets 1 Story for every team member buffed, so you need 3 turns to nuke. Cyrene's RMC buff makes it so when it's RMC's turn, he gets an enhanced basic attack which makes Cyrene immediately follow-up the enhanced hit with her nuke.
Can you run Cyrene without RMC and just use Tribbie E1? Maybe. But you'll notice a big drop in performance.
