I do it as Arcane Remnever and the pyrelord you can first off to start with hit him with slow spell to reduce his movement to 60% when the adds are near you then hit him with. Ring of Frost works like a hunter trap but only shorter.Once the images popped the adds are a piece of cake to clear. You should be able to kill at least 2 adds before Ring of frost is finished. If it's finished just hit him again with slow spell and then with frost nova if it's really needed unless just keep slow on him and blink away to finish that last add