This was quite a nuisance as an affliction lock. Ilvl 488.
Tried using a Grim of Sac harvest life build but found was I getting behind on adds too quickly even with that.
Tried using a combo of seed + harvest life, still no go.
Tried both above combos using Grim of Supremacy, Voidlord and Soul Link, getting progressively closer.
What finally worked was:
Grim of Supremacy, Void Lord, Soul Link. Used seed of corruption to clear birds, needing two seeds to clear each wave, so effectively casting a seed every second gcd and using the interim gcds to keep DoTs running on Yikkan.
Pre-potted, popped DS:M on the pull, used Unending resolve, Healthstone, and Mortal Coil (to interrupt screech).
Got 2 screeches, used Unbound Will on the 2nd since Mortal Coil was on CD.
Ended up being close but I got it