Just to second the information above, yes the magician aura affects all pets, including swarm pets. It may not sound like much, but the small percentage it adds can really makes a difference in your pet damage output. I know many magicians that do not use it, and I think they should, however that is not really a criticism as I fully support and encourage different playstyles. My only complaint is the range is a little short, and sometimes I have to get a little too close to the action to see it show up on my pet. I suppose this only matters because I usually run in an all caster group without a tank, but still...some mobs have huge hitbox ranges and it has killed or nearly killed me a few times tying to inch up until I see the aura hitting my pet. Getting too close to a heavy hitter wearing silk with nothing but pet tanks can be a dangerous game!
But in a group that usually consists of two magicians, two necros and a bard (who can fire off swarm pets in a burn or whenever he wants I guess) it gives us a pretty sizable increase in our dps. On a side note of happy-dance-inducing glee, just two night ago I finally got the rank II version of it while helping a friend farm in Underfoot zones. I know, I know, old news, but it never dropped for me. Now, I am happy to have it.