I recently got a Cold Heart, and was interested if anyone has an in-depth sense of how using Cold Heart impacts your single target rotation. E.g. how many stacks makes it worthwhile to cast.
My general assumption would be:
1. Always cast at 20 stacks (should be lined up with casting Pillar)
2. Cast again 20 seconds into Pillar (10ish stacks). (so you have 20 stacks by next pillar)
3. Repeat.
But I could see it working differently if at a certain number of stacks its just worth casting no matter what. Presumably your main concern is maximizing the number of stacks cast during Pillar, but I'm not sure how that interplays with longer Pillars (from tier) when also trying to maximize the number of stacks for the next pillar.
Also, I'd be interested if anyone knows of an addon that make tracking stacks simpler.
Or if you don't trust or want to use the string, here's how to make one yourself.
Display tab: Automatic Icon, Text, checked. Text is %s.
Trigger tab: Type is Aura, Aura name is 248406, Unit is Player, Aura Type is Buff, Stack count is checked (operator is <=) stack count 20.
Load tab: Player Class is Death Knight, Talent Specialization is Frost or Unholy (depending on what you're playing.)