Hmm...It might be you need a fighter in your party, someone who can draw heat away from the less armored fellows.
Healing spells aren't really very helpful in combat, because they cost an action to cast, or a spell slot that could otherwise be used better, so I'd keep it to potions.
It also sounds like you're letting people 'bleed out' you can use the "Help" action to keep them from dying, or you can even 'Throw' a potion at their body to heal them.
The only sticking point I can think you might be having in the crypt is perhaps you're making all your attacks with disadvantage because nobody can see in the dark down there.
