We talked about this a little bit in-game over the weekend... Some of the behaviors that I've noticed with the tamed dogs:
* If I attack a target with a ranged weapon, the dogs will sometimes ignore the combat completely. If, however, I attack a target with a melee weapon, the dogs are on that target like... a pack of dogs!
* If a thug/mutant attacks me, the dogs will just sit there happily watching me get beat down until I successfully target and attack the attacker myself.
* The dogs run (slide?) more slowly than the players, so it's possible to actually outrun and lose your own tamed dogs.
* Should there be a limit on how many tamed dogs a player can have? With three of them, I can run up to a thug, pop him in the head with the club, run away, and watch the dogs tear him apart in seconds.
* It'd be cool if the dog stayed with the backpack when a player dies and attacks anybody who tries to loot the pack. Another alternative, as suggested by TheBassernator, would be to have a dog actually pick up the backpack and start running in the direction of the respawned player; good doggie! :D