I will admit bias here, but I would choose a shammy also. The druid, will trump the sham in DPS with nukes and will out heal, but the sham with pet, pet proc spells (the puma line)will do better over time damage. The buffs that the sham can bring to the SK and slows on the mobs, will allow more battle time and less down time. It is nice that Dog can off tank for a bit if needed. Also, since you already have a snare with the SK, it makes the last 15% of a mobs life easy when Dog is killing them from behind and then returns while the SK is getting healed, pulling or what ever.
I would love to port but the druids have us hands down there. But since the SK can FD, and the sham can put Dog on the mob as a delay sacrifice to zone or gate, it isnt too bad.
Thats my .02!
Atomic