Giving them a search ability could be interesting. Use trained dogs to help track, maybe give them something that belongs to a player and they can ping if that player is nearby. Low cost tracking system.
I agree dogs in combat would be OP, but the idea of adding some kind of utility to them is kinda neat. Making them extremely perceptive, or some of them anyway, and good at searching items, detecting hidden people and sneaking people, audible barking from a room or two away if they detect someone, like a cheap alarm system.