Hey, Just saw the release date trailer.
I'm wondering, are you going to ship with the same character selection system? I feel like that's a mistake.
When learning a game most people stick with a single class, forcing new players to go form the default healer to a darkmender or a blood giver won't gel well with new players.
Personally I like random characters run so it wouldn't bother me, just looking at it from a newbie's perspective.
When allowing the player to select what they want you can also squeeze more replayability in the game if you make it so some healers have to be unlocked.
For example the blood giver could be gated behind being resurrected by your party. Or maybe the most niche healers could require you to clear some dungeons.
In games like FTL or the Isaac games people do runs to try unlocking characters and then a couple of runs with said characters to see if they like them.
Paradoxically, having all healers unlocked at the beginning makes me never want to play something like a darkmender or a sunmender.
The rest of the party being random is fine imo.
For the UI, since I understand the current one would do a poor job at letting you choose between all healers, you could have a room with 3D models that you click to select/deselect. Something like Dragon Age: Origins's party selection.
Healers could have their own room with hand placed models, locked ones being invisible or made into black silhouettes. On this screen you could also showcase little cockades or medals to show what dungeons you've cleared with each characters, giving completionists the satisfaction of seeing all their achievements laid out in front of them.
The rest of the party could be lined up in a tavern. Or maybe tanks could be in an armorer's room and DPS characters could be in a fighters guild type of environment with weapons hanging on the walls and such. I suppose to keep things uncluttered you'd have to select the healers first and then the camera would move to the tanks and then to the DPS, with big arrows to the left and right of the screen to change selection screen manually.
That way the player can immediately see all the available characters, the current UI where you need to select a class icon and then click confirm is a bit clunky anyway.
Regardless of how you approach the UI I think giving the player a progression goal in unlocking characters and not forcing them to play a random character every time would improve Healed To Death.
Cheers and good luck with launch!