There is a possible flaw in this, as we have ignored the probability of using Demonic Aegis in the Talent tree. That being said, the base effectiveness of your Fel Armor, which was 30%, is now increased by 30% (of that 30), making it equivalent to 39% of your Spellpower.

869 Spirit x .39% (which more than likely, most warlocks spec Demonic Aegis), would = 338.13 SP (unrounded).

That being said, 867 x.20 (Assuming LT Glyph) = 173.4 SP(unrounded).

These 2 would be equivalent to 511.53 (or 512) SP, and assumably the same math that drove motif's conclusion in the original comment.

A good way to calculate this is spirit being = to 59% rather than 50%.

I normally would, saving that the original calculation did not include, and specifically excluded buffs. I was trying to educate where the difference in math came about is all. Either way is a good way (and there is the small (extremely small) possibility a group may not have a paladin, so the most absolute way as well, as it will reflect the true base stat).

Any serious group that did not include a paladin would have the Drums of Forgotten Kings at only 8% but still better than nothing.

with 0/13/58, what is the magic border of spirit at which it's better to replace the LT glyph with the Immo glyph, looking at the massive loss of Spirit with the t10 gear

I did a VERY rough calculation on this earlier. Warlock: Simple Questions/Simple Answers

As your Spell Damage increases, the switchover point increases. I've actually stopped using Glyph of LT because

• the benefit was so minor,
• I would sometimes fail to maintain the buff,
• it required more healing for the increased use of LT,
• and not using it makes my life simpler.

If I get gear with alot of spirit, I'll switch back.

- Glyph of Life Tap essentially gives you an amount of spellpower, the DPS value for spell power is relative to the amount of haste, crit, and to some extend- spirit that you have. Additionally in the real world this glyph has a very real opportunity cost in the shape of requiring additional lifetaps to gain the buff. The oppertunity cost of this glyph to an extend inversely scales with the amount of intellect and spirit you have (More intellect = more mana regen = less lifetaps needed, more spirit = bigger life taps = less lifetaps needed).

- Glyph of immolate increases the periodic damage of immolate by 10%, this by itself is only effected by spellpower, however this glyph also translates into extra damage through conflagrate. The extra damage through conflagrate does scale with critical strike rating.

Basically what this means is... There is no magic border that will hold universally true for everyone, you're just going to have to try and run simcraft and see where the relevant border is for your gear specifically. Also consider the type of fight simulationcrat simulates, you might want to compare the glyphs on both a patchwerk and helter skelter settings as the oppertunity cost of glyph of lifetap is a lot more relevant when you're not fighting patchwerk.

I believe the wowwiki page is erroneously referring to the mana cost of the spell (57% of base). Anecdotally and by napkin, ROF does indeed get 33% SP/tick. (My per-tick numbers and stats are very similar to the examples used in this comparison.) On a similar note, SOC costs 34% base per cast, but its explosion coefficient is 21.3% SP as noted on the wowwiki pages.

(EDIT: I made a suggestion that Backlash was getting ignored in these calculations. It was pointed out that Backlash affects all spell schools equally, which would make any increase in ROF's DPT proportional. I removed that calculation.)

However: We are also ignoring Empowered Imp procs. Every time the imp crits (assuming he starts attacking when you do), (EDIT 2: Tested this...) your next SOC explosion or tick of ROF is a guaranteed crit on all targets. Considering that a raid-buffed imp with pet crit bonus from tier probably will proc this once every 10s or so, this is a significant bump to ROF's DPS and should close the gap somewhat. It also boosts SOC significantly, so it ends up not changing the proportion except insofar as the crits on ROF have a higher multiplier.

I'm still a little hung up on the mana throughput as well; ROF is 2198 mana/6.8s (at my haste level); Cataclysm knocks another 10% off to make it 1977/6.8s. Meanwhile, SoC uses 5244/6.8s (to be fair, 4929 if you happen to have Suppression). If you really wanted to game the system to save mana, you could seed until EI procs, do a single ROF, then go back to seeds until you see EI come up again.

(Did we just invent AOE weaving? Ugh.)

You understand me completely. (In that I totally let that 'all spells' go over my head.) :p Good catch. I'll have to carve that out.

If that's so, it more or less removes Backlash as a contribution.

EDIT: Checking how EI works, I just went ahead and tested this out in an instance, and each tick and explosion are indeed considered to be a separate spell hit chance (EIs that proc mid-ROF crit the next tick, and EIs that occur when a seed's in flight cause crit-plosions.) This actually boosts the DPT for both spells considerably because it makes full use of the EI procs (it also makes it necessary to model EI uptime to figure out how much it does so). That means that the only consideration turns out to be mana usage, which is significant in a long AE pull or boss fight but not necessarily a deal-breaker.

Greetings
You are correct that I prematurely rounded, thank you for the correction!
Now that I can verify in game the spell coefficients, at sufficiently high levels of spell power, RoF will do more damage than SoC. With that said, those levels are not sustainable levels in game at this time.

I have 3041 spell power with no procs, self buffed with Fel Armor. I took off any trinkets and did not life tap. I left the imp on passive.

My gear has changed slightly since the original post.
Collecting a small sample, I obtained (after removing crits) on an 80 target dummy.

2648
2562
2760
2672
2610
2672
2591
which averages 2645. This isn't enough to verify the spell power coefficient, I just wanted to verify I had given accurate numbers.

1779 was my dmg for RoF with that 3041 spell power

Base RoF is 3112/4 = 778 (not 375). I confirmed this in game by testing it's damage naked on a target dummy.

Using the assumption of actual spell dmg being calculated as
non crit spell damage = (Base damage + (Coefficent * Spell Power))*talents*(% dmg multipliers like CoE)

we obtain coefficient = (non crit spell damage - base damage)/ spell power since I had no damage multipliers up, and no talents boosting the damage.

This calculation confirms RoF coefficient is indeed 33% per tick. I corrected the wowwiki RoF article I linked in my original post to specify 33% / tick.

The same calculation gives 28-31% as a rough estimate of the coefficient of SoC, which is in the same region as the previously mentioned values.
I realize that Spell power coefficient - WoWWiki - Your guide to the World of Warcraft lists the spell coefficient of SoC as 25% for the AoE, but this can be seen to be slightly incorrect using the process described on that wowwiki's discussion page. Restating the process, using the maximum damage and working back to the spell power coefficient gives a lower bound for the coefficient of 28%.
Similarly, we can find an upper bound using the minimum damage of 31%.

So, Seed of Corruption does scale slightly less well than Rain of Fire. Thus, my previous statement that SoC would always dominate RoF (ignoring mana considerations) is incorrect. At sufficiently high levels of spell power, RoF will do more damage than SoC. I used an estimate of 29% for the spell coefficient to Seed of Corruption to find the threshold, but the expression is easy to derive in general which I will do below.
The threshold decreases (nonlinearly) as crit increases, but is up in the spell power 7000+ range for crit about 40% and 5000 spell power range for 70% crit. The base damage for RoF is just so low, and coefficients sufficiently close, that even at the extreme case of 90% crit, about 4390 spell power is still needed for the threshold.

Rough supporting mathematics:
Let be the spell power coefficient.
Let be the base damage (per tick for RoF, explosion for SoC).
Let p be the spell power.
Let be the multiplicative talent modifiers, and multiplicative damage modifiers.
Observe is the non crit damage from spell i.

We also define a few intermediate variables to ease notation.
Let - weight including the talent and damage modifiers
- weight excluding talent and damage modifiers.

So, the AOE dmg for spell i is
.
We seek to find the spell power value p at which .
Setting the two expressions equal and solving for p, we have


Scanning the list of talents and damage modifiers, it looks like . With that assumption as a special case, we have

giving the desired threshold for spell power for RoF to dominate SoC.

Going through some examples




Plugging in c_s = .3 and c_r = .35 gives
and , and so p = 8920 would be needed for RoF to do more AOE dmg than SoC.

The threshold is nonlinear as a function of c_s though, so c_s = .4 gives p=7166 as the threshold and c_s = .5 gives p = 6328. This reaffirms that certainly in 5 mans and solo, SoC > RoF. As far as I know, these are not currently attainable gear levels for spell power. Empowered Imp effectively increases the crit rate, although it's not immediately clear by how much, and that indeed that lowers the threshold value for spell power. Even with a massive c_s = .7 as the crit rate, we still have p=5161. Correct me if needed, but 5161 spell power is only achievable with full raid buffs, near BiS gear and trinket procs. On the bright side for Rain of Fire, if any talents or buffs give a multiplicative boost to Rain of Fire but not Seed of Corruption, that brings the spellpower threshold lower. Further work on pinning down more precisely the spell power coefficient for SoC would also be useful.

I'm holding off on considering mana until we have the pure damage situation clarified. As always, corrections and feedback are welcome.

Thanks for answering my questions and for going so much further. I haven't read through your answer with the thoroughness it deserves because I'm at work, but I will.

I got the 375 from the spell's tooltip, and then screwed up my math. According to what I read it was 2700 base damage for 4 ticks, which should have been 675 If I could divide properly (why I got 375 I don't know). This is of course before all of the talents that boost fire damage, which explains why you got 778, or the spell's mis-documented.

N.B. A basic failing of mine: When I read or reply to messages here, I'm not near my game machine, and tend to answer based on numbers from wowhead and wowwiki which I usually accept as gospel, and simcraft and other posts here which I usually accept as "Very likely true" or "True enough"

source

Would it be a nice buff?