Updated for Patch 5.2 as of March 11, 2013.

With the buff to the damage of Divine Star in 5.1, there has been a lot of discussion about when it is appropriate to use it in lieu of Halo or Cascade. Each has a different cast time, mechanics, and damage out put that make some better that others depending on the encounter mechanics such as number of adds, distance from the boss, and movement. For this post, we’ll stick to single target encounters.

First and foremost, lets look at the maximum percent damage done by each spell, based on the distance from their target:

As you can see from this graph, Divine Star does its optimal damage no matter the distance from their target up to 30 yards. Damage for Cascade starts at 40% and increases by 2% every yard in distance until it reaches a max of 100% at 30 yards. Damage for Divine Star is assuming that the target gets hit twice: once on the way out and again on the way back. Halo uses a custom function that determines its damage based on how far from the target you are when the spell is cast; the optimal distance to be from a target is 25 yards.

On a per-cast basis, this means that the damage done (based on distance to the boss) looks like this:

Please note, Crit has been omitted from the values for clarity because the crit chance and crit damage increase is the same for each spell.

There isn’t anything shocking about this chart: Halo does the most damage at its optimal range, followed by Cascade and Divine Star. This holds with what is expected, with the highest damage being the longest cooldown (Halo, 40sec) and the lowest being the shortest cooldown (Divine Star, 15sec).

When we look at how much damage is done per second (DamageDone/Cooldown), the values change quite a bit:

As we can see, Divine Star takes the lead in DPS on a per cast basis while Cascade ties Halo at their respective optimal ranges. “But Twintop,” you say, “this is for 35000 Spell Power. What if I have more/less Spell Power?”

I’m glad you asked:

As you can see from this graph, Divine Star outscales the others handily by gaining almost 700 DPS per 10000 Spell Power. Cascade barely outscales Halo, though only by about 30DPS at 30000 Spell Power. With this data in hand, it makes our decision about what Level 90 / Tier 6 talent to choose simple: Divine Star in a landslide! …or does it?

One concern that has not been addressed yet is the number of GCDs required in order to get this DPS from your chosen Level 90 / Tier 6 Talent. The more GCDs you have to use, the fewer GCD opportunities you have to use other abilities. Comparing the number of GCDs used per minute for these three talents:

Divine Star takes 2.67 times as many GCDs per minute to do the DPS listed above, compared to Halo, while Cascade takes roughly 1.67 times as many GCDs as Halo to achieve lesser DPS results (than Divine Star). What this effectively means is that Divine Star uses 1.67 more GCDs and Cascade 0.67 more GCDs every minute than Halo does, sacrificing other ability casts in the process. For a ‘best case’ scenario let us assume that those extra GCDs, over the course of an entire fight, would have been Mind Flay casts instead. We need to remove this damage from Mind Flay from the total damage done by Divine Star and Cascade in order to get a clear idea of how much damage Halo is doing in comparison to what the other abilities do [i]in lieu of[/i] Mind Flay for the extra GCDs:

If you’re at optimal range, or at least 20 yards away, Halo will do more damage per GCD than Divine Star or Cascade. Interestingly, Cascade does [u]more[/u] damage per GCD than Divine Star does once you are at least 25 yards away from your target at 14.4% (baseline) Mastery. This bring up another very important and interesting effect: as Mastery increases the number of Mastery procs from Mind Flay also increases, meaning the DPS Damage per GCD drops! In the above graph, the drop in damage is more pronounced between 14.4% Mastery and 30% Mastery for Divine Star than it is for Cascade.

You can see this disparity increase as Spell Power increases:

Halo‘s DPS edge over Cascade increases from 90 DPS at 10000 Spell Power to nearly 300 DPS at 50000 Spell Power. Additionally, looking at just the effect of Mastery on Divine Star you can see the DPS difference go from ~70 DPS at 14.4% and 30% Mastery at 10000 Spell Power to ~300 DPS between 14.4% and 30% Mastery at 50000 Spell Power.

In summary (for 1-target fights):

• Halo is still by far and away the best DPS choice just as long as you can maintain at least 15 yards distance from your target.
• For very close quarters, Divine Star does the most damage.
• If you are closer than 15 yards away or need clumped up and consistent/often occurring raid healing, Divine Star is the best choice.
• If you are further away from the boss (more than 30 yards), Cascade is your only option.
• Mastery increases the disparity between the Level 90 / Tier 6 talent choices.