If healing is essential, but no cleric is present, everything gets a lot easier with minor magic items, wands especially (as has been mentioned). I am playing in a party composed of a sorcerer/incantrix, scout/nethar hunter, ranger/tempest, and a druid/sorcerer/arcane hierophant. Everyone has a wand...druid has some healing spells but suffers from the same spell progression problem as a mystic theurge build. We have to be very wise because the ranger is the sole meatshield, if you could call him that. We depend exclusively on mobility and stealth in combat. Several combats have ended with days of resting.
No one has mentioned it yet, but the Heal skill comes in useful if you are cleric-lite. You can really accelerate the healing-while-resting technique with some good Heal checks.
