Rift Mob:Rorf  

Normal Mode Strategy

Preparation
Before you pull Rorf Make sure you have killed the three Wanton Sentries before you pull him as well, These mobs will run and summon more mobs, only one at a time will be visible and once one is killed the next will spawn until all three are dead.

Encounter
Rorf is a very simple fight once you reach him. Rorf and his pet Sneaky patrol around the room in a half circle. After you pull him have your tank pickup both Sneaky and Rorf.
Sneaky should be focus fired down first however Rorf will not enjoy seeing his pet killed and he will cast a Channeled Spell to Sneaky which heals him over time. You can either out dps this or take the easy route and have someone interrupt Rorf. With the dps you have at level 42 you can expect around 3 interrupts to occur before you defeat Sneaky. After Sneaky is dead then focus fire down Rorf and collect your loot.

Expert Mode Strategy

On Expert mode, Rorf has three adds instead of one. The strategy that seems most effective is to pull all of the adds together behind the pillar in the center of the room. Rorf moves very slowly around the pillar to get back into line of sight of you and his pets. While in line of sight, Rorf will shoot spectral pets at random targets for 1500+ damage, so make sure you aren't visible to him. When the pets drop below 50%, he will start casting a channeled heal on them from time to time, which can be interrupted to speed up the fight. AoE down the pets, the order doesn't seem too significant. When the pets are all dead, focus the boss.

An alternative method (should your healer and offhealer agree, offcourse) is to simply stand there taking all the damage to the face, and nuke him down. Obviously this will cause quite a bit of stress on your healer, and will most likely not work properly in the average PuG. Be aware that he randomly teleports around the room as well, meaning you need to move his pets towards him every now and again. And don't forget to keep interrupting his heal! It's a fairly obvious casting animation of him pointing his spear towards one of his pets, and as a tank this is easily interrupted.

Rorf, Droughtlands, Lantern Hook

This is the Rorf in our "proper" timeline. In the alternate timeline instance The Fall of Lantern Hook, Maelforge has corrupted him and he becomes a boss encounter with his three "kittens". He is a kobold, not a dog, but he is the sort of kobold who might have a chew toy.