Because they can do 800k NS healcrit inside an arena. (I know I made one last week, my thought was that it's really balanced combined with our mastery)
tremor totem for fears
grounding totem for spells, you can ground a grip, ground a HoJ
earthbind for AoE slow
windshock for interrupt
earthshield
riptide is instant
healing stream totem
shaman mastery means you can gem spirit instead of pvp power since the lower the hp of your target the larger heal you will put out, therefore you get better mana regen