Legendaries - you'll want to have sephuz here, legendary legs will do fine (i ran with these two) and then changed sephuz to legendary wristst for burst phase
Talents: Typical BOS Build but with White Walker and Blinging Sheet (for surviving arcane phase and bonus interrupt/cc)
http://eu.battle.net/wow/en/character/burning-legion/Huion/simple
Food: Bear Tartare (bonus movement speed after killing icycles and mirror images - its crucial since we need wraith walk for special moments)
1st phase - save your cds mostly for icycles, you can then kite (after interrupt) xylem near them to get free dark succor proc)
my way:
1st icycles - Pre AMS them (you should pop BOS when you engage bos, so you dont need any extra cds)
2nd icycles - pop sindra
3rd - try to get some GS stacks before them, pop pillar and kill them normally
4th - i had sindra for them (thanks to legendary legs) but if you dont have, just drink prolonged and you shoul'd be fine
2nd phase - kill one mirror, get healing, then pop AMS and Wraith Walk to get to Xylem (its crucial to have cds for it)
3rd phase - just avoid orbs
Dont forget to interrupt a lot - try to save Death Grip for every teleport hes doing, not for interrupts. You can use Blinding Sheet to interrupt arcane phase (or just overheal with death strike).
And for healing - i almost never used frost strike, 95% of my rp went for healing.
AT THE TRANSITION TO 4TH PHASE YOU CAN EAT AND CHANGE GEAR
4th Phase - After you engage boss DONT pop cds. Adds are really prio there.
1st adds: bl, pillar, hwr and BOS
2nd adds: sindra
3rd adds: prolonged potion + pillar (dont forget the slow proc from remorseless winter)
4th adds: i had trink from elisande so i could pop HRW here, but yo ucan do this with just pillar and BOS