Positioning is ok. We do try to get the orb as soon as it pops. We have had some issue of our taunt being on CD because of the switch, or just not targeting it easily.

The disc priest does good at keeping the tanks up. With my shaman I chain heal when need and I Riptide a tank every time I can. I also spam LB with him between orbs and whiteout, on occasion.

Everything goes well until about 50-55% (I think that's after 3 whiteouts, maybe 2) but a Frost Nova hits or an orb gets too close and we lose my group (the lesser GS team). We may need to tweak our tank healing as getting more than 4 stacks (in the rare case of a missed taunt) almost always dooms a tank.

We both use macros from this site. Mine may need to be tweaked to account for haste on new gear, etc.

Frost Aura, check! We also tried dropping Frost Resistance totem, since we have 3 shaman total.
Healing Stream, I KNOW we have one, and I think two. I am reminded that I may need to do a better job of re-dropping the totems. Mana Tide eats my water one and Fire Eles eat the fire totems. I'll watch for that.
We've tried both. It seems to work best when we add \targetexact Frost Orb or some variation. We both use ISBoxer so it assists the tank even if the \target fails. It seems like the dps pick up the orb faster with the target in the macro.

We may try the suggestion I have read a few times now; the tank not on the boss pick up the orb and only his group dps it down. It will take longer for it to die but we may be more sure about picking it up.