The initial change
There isn't any easy way to put it, so it's best to come right out and state the changes:
Insect Swarm now generates 8 Lunar Energy for druids with Eclipse.
Moonfire now generates 8 Solar Power for druids with Eclipse.
Sunfire now generates 8 Lunar Energy for druids with Eclipse.
First off, the wording on the change was rather confusing, and understandably so. Usually when Blizzard uses the phrase of Eclipse, it means when one of the buffs is actually active. In this instance, that wasn't the design intent; instead, it means just druids with the Eclipse mechanic itself. The patch notes have since been amended to say for balance druids, to clarify this.
What does that mean, though? Well, it's a little tricky. While you have Solar Eclipse active, both of your DoTs -- Insect Swarm and Sunfire -- will generate 8 Lunar Energy upon cast. Once you leave a Solar Eclipse, Sunfire is no longer active, instead switching back to Moonfire. During this time period, Moonfire only generates Solar Power; however, the Eclipse bar is locked moving towards the Lunar side, causing the Eclipse gains from Moonfire to be negated.
Insect Swarm, however, will still generate 8 Lunar Energy on cast. On the flip side, once you proc a Lunar Eclipse, the energy gains are reversed. Insect Swarm still only generates Lunar Energy, but with the bar being locked, those energy gains don't get factored in. Instead, only the 8 Solar Power gained by casting Moonfire is tacked on.
What does this all mean? Well, it means quite a lot of different things, and each of them impact us in radically different ways.
Losing Eclipse: The single-target rotation
In terms of single-target damage, not all too much gets changed. Remember that Eclipse is a system that is based upon the number of spells cast, with each spell contributing to the total energy needed in order to reach the next Eclipse. In the pure rotation, this change doesn't carry too significant of an impact.
Previously, a balance druid would cast a single Starsurge
and five Starfires
during a Lunar Eclipse. Starsurge is worth 15 Solar Power, which would bring you to 85. Each Starfire is then worth 20 Solar Power. After four Starfire casts, you'd be left with 5 Lunar Energy and still sitting in a Lunar Eclipse, which means your fifth Starfire cast would still benefit from the proc.
Now, after this change, this will no longer be the case. You will have to cast at least one Moonfire during any given Lunar Eclipse. When combined with a Starsurge, this would put you at 77 Lunar Energy -- just enough for four Starfire casts before the proc ends. In effect, this change removes a single Eclipsed Starfire cast from our rotation.
On the Solar side of things, it's a little bit different. Currently, the same standard rules pretty much apply. Normally, you will get a single Starsurge cast off during an Eclipse proc. Since Wrath
generates 13 Lunar Energy per cast, this means that after your Starsurge cast, you have seven Wrath casts until Eclipse ends.
During each Solar proc, though, you will have to cast at least one Sunfire and one Insect Swarm. This contributes a total of 16 Lunar Energy to the pool. When combined with Starsurge, this leaves you with only 69 Solar Power left in the Eclipse, or enough for six Wrath casts. Again, this equals a loss of a single Eclipsed nuke cast during each proc.
Gaining Eclipse: The single-target rotation
Now here is where things can start to get a little bit more complex. Our losses in Eclipsed spells cast is a direct nerf to our damage; there is no arguing this. The issue on this change, however, is whether or not it is an overall nerf. We may lose Eclipse faster, but if we gain Eclipse faster in contrast, then the net change is neutral.
This time, we'll start with Solar. With only a single Starsurge cast, you'll end up casting Wrath a total of 14 times before you get a Lunar Eclipse (remembering that 7 of those are buffed). Now, after this change, with only a single Insect Swarm and a single Sunfire, that changes to exactly 13 Wrath casts in order to reach a Lunar Eclipse (six of which are buffed).
The hiccup is that a single cast of DoTs won't usually last this long; you'll have to refresh them at some point in time. Now, assuming you refresh outside of Eclipse so that you have Moonfire and Insect Swarm, this only results in a gain of 8 Lunar Energy. The downside of this is that despite Insect Swarm's generating Lunar Energy itself, it doesn't reduce the amount of Wrath casts needed in order to reach a Lunar Eclipse; you still need 13 total Wrath casts.
Due to this, for every single Solar Eclipse, you absolutely must cast either Starsurge or Sunfire twice. With Shooting Stars
procs, this shouldn't be an issue, and even without them, Starsurge will naturally fall off cooldown before you reach a Lunar Eclipse. The problem with this is that it could occur too close to the Lunar Eclipse proc, and you want to cast it during that time frame.
This leaves you with only one option: double-casting Sunfire. If, before your Solar Eclipse ends, you do not get a Shooting Stars proc, then there's a little trick that you have to abuse. On your sixth Wrath cast, which will force you to drop a Solar Eclipse, you will have a fraction of a second during which Solar Eclipse is going to end yet is still active. During this time, you need to refresh Sunfire. Doing so does two things. First, it reduces your number of Wrath casts needed to reach Lunar by one. Second, it means that Sunfire will be up by the time you reach a Lunar Eclipse.
That little fun time over, it's on to the Lunar side of things. With a single Starsurge cast and a single Moonfire cast, you need to cast nine total Starfires in order to get to a Solar Eclipse. The downside here is the same as with Solar. A single Moonfire won't last the entire time it takes to transition from Lunar to Solar. Also, once again, a second Moonfire cast won't reduce the number of Starfires needed in order to reach Solar; you will still need to cast Starfire nine times.
The unfortunate side of the Lunar Eclipse cycle is that an additional Moonfire cast won't correct the issue. With a single Starsurge and two Moonfires, you are left with 169 Lunar Energy to expend before you reach a Solar Eclipse; another Moonfire cast would merely put you at 161, and you need to hit 160 or lower in order to only need eight Starfire casts.
All of this means that you need to cast Starsurge at least twice per Lunar rotation in order to reduce the number of unEclipsed Starfire casts down by one. As with Solar, this isn't an issue. You should get a Shooting Stars proc at some point in time, but even if you don't, there should be enough time in order for the cooldown to come up naturally.
Due to this, it is highly imperative that you ensure you can cast Starsurge as close to the start of every Lunar Eclipse as possible. This makes prioritizing Starsurge a very wonky and gamey system -- there are very specific times frames when you need to hold on to Starsurge and when you need to cast it.