Remember to invest in Mashu's skills. She (needs to at least finish Camelot) + Merlin + literally anyone else can complete the stage without casualties. It got to the point that I left Drake and Nightingale alone since the latter is a healer and the former helps replenish my NP.
Though RNG can still screw you over so it might take a couple of tries.
Her presence consealment is so good, a lot of us couldn't find her in our Chaldea
Furthermore, it's more common than not for people to lack one of the Big Four supports- Waver, Merlin and Skadi. As a result, the support slot in a party is almost always dedicated to one of these four instead of a damage dealer support. There are exceptions, of course, but as a rule you'll fill that slot with one of those four. If you go in blind, you don't change that up until *after* the fact.