First, yes, you can still have a character hang out by a healing station. Us, for example, can sit by the healing area in the room where you get Shadowheart. That works.
You can also have someone in the room right before the helm at that healing station, but the cambions that spawn have the potential to see the character and engage in combat, so it's usually better to do it from Shadowheart's room. The game won't end if you have one of your characters out there. (Of course, if a character in the helm area tries to leave, the game ends....)
I never do that these days. It feels too meta and I suppose "cheesy" to me.
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Another tactic is to just keep the mind flayer alive. I don't use Shield of Faith though, or I should say I rarely use Shield of Faith. That's a spell slot that's generally better saved for a heal or a guiding bolt.
Instead, I try to throw healing potions at the mind flayer and attack the commander, often with attacks that give conditions. Lacerate to create a bleeding effect, for instance. Daze to lower the commander's saving throw against Wis. Command to force the commander to drop his sword. Guiding bolt so that the next attack against the mind flayer has advantage. All of those attack types should be saved for the cambion, not wasted on imps and boars.
In addition to throwing healing potions at the mind flayer, maybe a well timed speed potion, as well.
Protection from Evil and Good is useful if you happen to have it available.
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Is stealth becoming a full action? Did I miss an announcement?
Doesn't bother me if it is. I find that I actively try to avoid using stealth as a bonus action, in combat.
