Recently posted in the community forums:
“ Spark Bots on Mekkatorque were a lesson for us on the experiences of players who don’t have the option of using voice chat. Since then any time we make a mechanic with “hidden information” or other puzzle elements that require players to communicate on the fly, one of our requirements is to confirm through playtesting that it can be reasonably completed without using addons or voice chat. In Shadowlands this requirement has been applied for fights like Mistcaller, Hylbrande, Fatescribe, and Lords of Dread.”
Lords of Dread is absolutely not playable by a casual raid without addons or voice. Communicating in time as to who sees what and counting both to four is too slow, especially on Heroic.
If Blizzard feels that this is a good design for a mechanic, I implore them to rethink their position.