A Use for Eclipse

Yesterday, I made a big post about how Eclipse was still a bad talent despite how Blizzard was buffing it. For the most part I still stand by that post. The Precasting method is still a horrible way to use the talent, and I don't see any reason to put a full three points into the talent.

However, Erdluf (a reader of Gray Matter) brought up a really good point over on the Moonkin Repository. Find his post here.

His idea center's around using the Opportunistic method and ignoring the extra DPS provide by the Glyph of Starfire. Erdluf presents a very compelling argument that investing a single point into Eclipse can significantly increase Moonkin DPS.

Stat Assumptions:
Spell Power: 1800
Haste: 9.17% including Celestial focus and Imp MA
Hit: Capped
Crit SF: 37% - Includes Imp Scorch, MA, Nature's Majesty, and Imp IS (not unreasonable assuming a 15% base from stats)
Talent Build: Link

Can we ignore the Glyph of Starfire?
This is the first question we need to answer, and I think the answer is yes.

Lets remember what Glyph of Starfire does. It increases the duration of your Moonfire by 3 seconds thus adding another tick of damage. This is great in that it prevents you from having to recast Moonfire. In fact, if there are few or no interruptions in your casting cycle your Moonfire's duration will grow over time. Take this example.

Lets say you start a fight by casting Moonfire and then you spam Starfire. The global cooldown is 1.374 seconds long and Starfire will take 2.579 seconds to cast on average. In one minute you will be able to cast Starfire 22 times after the first Moonfire ((60 - 1.374))/2.579 = 22.73). Those 22 casts of Starfire will add 22 ticks of Moonfire to the original 5. So, over 60 seconds with a Starfire spam rotation you will build up 27 ticks of Moonfire, but only use 20 ticks. Therefore, over 60 seconds of Starfire spam we will gain 2 Moonfire ticks after you subtract out the original 5.

Since we will be building up the Moonfire ticks over time, it is reasonable assume that we can take brief brakes and let some of these ticks get spent without refreshing new ones. Otherwise some ticks would be wasted since Moonfire is likely to still be ticking after the Boss is dead.

Therefore, I agree with Erdluf, in that it is reasonable to ignore the Glyph of Starfire when evaluating the value of Eclipse. As long as the brakes are short and don't happen to often, having to recast Moonfire should still be fairly infrequent in long fights.

Unglyphed Starfire vs Eclipse Buffed Wrath:
An unglyphed Starfire will have the following DPS.

Avg DPS = (((1120 + (1800 * 1.2)) * 1.19) * 1.37) / ((3 - (0.5 * 0.37)) /1.0917) = 2074 DPS

An Eclipse buffed Wrath will look like this on average.

Avg DPS = (((588 + (1800 * 0.67)) * 1.42) * 1.34) / (1.5 / 1.0917) = 2484 DPS

This indicates that a buffed Wrath does 19.79% more DPS then an unglyphed Starfire. Therefore, given these assumptions, switching to Wrath from Starfire, can provide a significant boost to DPS temporarily.

Is the buff worth the talent points?
Now the question is can we get that buff often enough to make it worth the investment of talent points.

With only one point invested Eclipse each of our Starfire crits have a 33% chance to proc Eclipse. With a crit rate of 37% that means each Starfire cast has a 12.21% chance to proc the buff. Meaning, that on average it will take 8.19 starfire casts over 21.12 seconds to get the buff. Add this to the 40 second cooldown, and we see that the average buff cycle will last 61.12 seconds.

As we all know the buff's duration lasts 10 seconds, but it will probably take another Starfire cast to recognize and use the buff. So, the usable buff duration is only 7.421 seconds long.

In that time, you should be able to complete 5 wrath casts (7.421 / 1.374 = 5.401). These 5 casts will take 6.87 seconds to cast, and the buff will be up 11.24% of the time (6.87 / 61.12 = 11.24%).

Therefore, a single point investment in Eclipse is theoretically worth 2.22% increase in total DPS. Even if you miss the buff 50% of the time it will still increase your DPS by over a percent. In my opinion this is big enough to invest a single talent point in.

If one point is so good, why shouldn't I invest more?
The reason is the cooldown. It is the biggest factor in determining what the buff's uptime and it cannot be changed. Adding a second point will increase the the buff's up time to only 13.59%. This means that the marginal increase to total DPS for the second point is only0.469%. The third point is even worse.

On top of that, each point you invest you will cause you to cast Wrath more often and increase the likely hood that Moonfire will fall off the target..

Conclusions:
1. Investing one point in Eclipse can provide a significant increase to total DPS assuming that it doesn't cause Moonfire to slip off the target.

2. Investing more then one point in Eclipse is a waste, because the marginal gains for the second and third point are very small.