MAJOR SPOILER ALERT...
Just finished reading HARBINGERS, one of the best RJ books yet!
I also am glad that Jack didn't go to Europe to switch identities, "Repairman Mirko" just doesn't have the same elan...
After R slaughtered the Oculus and the Yeniceri, I was suspicious about Diana, and whether she was all she seemed to be after the Yeniceri found her unharmed in the next room. Given R's capabilities as a shape-shifter, and that he has, after all, taken the shape of a female before. As R appears later in his own form, and given the events at the end, it seems like just a subtle head-fake by fpw. I think.
Re the significance of the dogs, it could just be an efficient calling card - a woman alone in different guises wouldn't be as instantly recognizable to Jack.
I think it may be that dogs are our closest contact with the natural world. With cats and horses close behind in the running, they are the species with which we have the closest symbiotic relationship. A woman with a cat might bring unwanted Wicca connotations, and a woman with a horse would be unwieldy in most situations.
I always liked the legend (said to be Native American, but I doubt it) from an old Classics Illustrated comic about how God decided man was too close to the animals so he caused a great chasm to open between man and all other animals. All the other animals began to walk away from the widening gorge, but at the last moment the dog leaped across the chasm and landed at man's side, where he has stayed ever since. That's kind of the feeling I get about dogs - they're our interface with the animal world.
Another thought - maybe it is the dog who is calling the shots and the lady who is the dog's mouthpiece...
"Flow with the Go."
- Rickson Gracie