A problem with SoTA.

Hi!
The thing is that i cant play SoTA at all with my shammy.
Because when the battle beggins my screen goes down to 1 / 2 fps! Actually works all fine when im on the boat or waiting at the beach, but when the battleground starts, boom 1 fps.
Ive said "with my shammy" cus i can play it normally with my rogue and other characters, its like my shammy its doomed or something.Ive reinstalled wow already but this issue survive against all odds.
And this started to happen when the new core situation.
I dont know what to do and its pretty annoying when u got 3 SoTA when queued to random bg.
Anyone having the same bug? or knows how to fix it?
Thanks already B^)