If you can bring another Shaman the fight will be very easy A glyphed grounding totem absorbs all the damage during Getaway. Since you only have one I suggest you put the ScaryFog people into the group with shaman, and anyone who doesn't have good self-heals. To answer the OP though, I think a DK is good enough for both specials. During Getaway he can just pop Pillar of Frost (glyphed I presume) and nuke the boss freely because it makes him stand still.
Does the shaman need to drop the totem before the boss start casting get away? or can he drop it during get away?