The crystal bag is nice to have, but certainly not essential.
The dolls are very useful as mules, and somewhat useful in other situations. The act 1 skeleton doll can equip a crossbow, so can provide good support if kept out of the direct combat (I only bothered doing so for the toughest fights), and any doll can provide a temporary distraction (even if upgraded they are not that tough). Dolls can trigger area effect traps, clearing the way for your main characters (they can not open trapped containers, though).
