Some guildmates mentioned that the drop rate of the Maelstrom Weapons in Vma is after dark brotherhood 100%.
I can't find any mention in the patch notes so I ask here
No.
Drop rates will be 50% weapon 50% jewelry at the stage 9 chest. Weekly rewards will still have 100% for a weapon and an additions 50% chance for a jewelry piece.
All other chests in vMSA will have a 100% chance to drop a set item.
To lazy to search the source but it was an official statement in one of the MSA threads.