ok we did the hard mode last night.
We had a shadow tank and a guardian on the boss
we had out least laggy sage setup to pull the shadow.
thermal cast starts
guardian takes boss
shadow burns cds and stealth
shadow hides behind pillar
stacks wear off shadow takes boss back
we tried just using two tanks but found that we just needed a third one for add kiting duty on that second set of adds.
That was what worked for us.
It's doable with two, although three might make it easier. Were you doing 8-man or 16? In 8-man I wouldn't give up that DPS spot for a tank, but it's a bit more forgiving in 16.