I have a halfling paladin that uses ride-by attack with spririted charge (and, by the way, wears Rhino Hide armor). Because he's a paladin, he also uses Divine Might - with his charisma of 20, that +5 damage.
Of course, charging is x4 damage for him, so, adding his +3 from STR and +3 from the lance's bonus (he's 13th level, so it's appropriate), he does +44 damage each strike, +96 once per day when smiting evil. That's not counting Power Attack or any othe damage boosters.
A regular fighter could optimize for criticals to further increase damage to X6 - a paladin does not have the feats to spare.
At this point, the bite from the dog doesn't mean much, so I don't worry about offense for the dog, I worry about defense - a dead mount is NOT a good thing!
Generally speaking, the proper mounted tactic is to use Ride-By Attack (hopefully with Spirited Charge as well) to deliver excellent damage, and don't get the mount directly into melee combat. Mounts tend to be rather fragile, and must be carefully protected.