^Ironically Dog is an even better bluffer than Leliana. He can make it past all of the speech checkpoints in that quest. So choosing Dog to rescue them actually makes perfect sense.
I call unfair play here Loghain and E-Man just tell me WHY in detail I can't use my Dog to decide the fate of this Dog-realm!?! You know what let the Darkspawn take you all to the Void!