Katie, I'm not a vet, so for the best advice, you should contact the great people over at the U of I wildlife clinic:
http://vetmed.illinois.edu/wmc/
What I can tell you is that baby rabbits that have been attacked by a dog often do not survive, even if it appears that they have no obvious injury. There can be internal bleeding or broken bones (i.e., punctured lung) that you wouldn't be able to detect just by looking. There are also possible infection issues, even small cuts combined with being in a dog's mouth can spell trouble. And then there's the stress of being attacked and removed from the nest.
It sounds like you did everything right. Put them back in the nest for mom to feed. Kept it warm when you removed it from the nest. It was just too far gone at that point.
But I really do recommend talking to the vets/vet students at the clinic. They are a fabulous resource and always willing to share what they know.