If it’s Moira then the mode will have two healers (Maybe 3 depending if health packs are a thing in the mode)
If it’s not Moira, then if it’s heavily implied Baptiste would be the only solo healer. Which matches with Archives and Uprising having one healer.
It would be interesting to see what skin the last persons for.
Or it could be an elaborate bait and switch and you play as Roadhog, Symmetra, Junkrat and Lucio