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Old stuff Edit
Concerning the classic SM/Ruin:
The most common setup I've seen that is (from my view of the mechanics) used improperly is the old SM/Ruin build. On the 60 system, this was quite a valid build but when applied to the 70 talent list it simply fails to provide the best possible DPS for low to middle tier raiding warlocks.
Addressing Shadow Bolt alone:
C = Number of Crits per 10 Shadow Bolt CP = Crit Power N = Normal hits NP = Normal Power
C(CP) + N(NP), simple stuff, this is a comparison of a Shadow Mastery/Demonic Sacrifice/Bane setup (30/21/10) vs. SM/Ruin stock. Given this is a raid comparative and any buffs/debuffs applied will be present for both setups they are considered moot and removed from the calculation. The calculations include all pertinent buffs as moot (including SM, which is present in both setups) and is simply comparing the delta of notable talents from each setup. For Shadow Mastery/Ruin the talents are Ruin and Devastation. For DS the talent is simply: Demonic Sacrifice.
Scenario #1 is a stock raid lock with sufficient +dmg to deliver 2k sbolts, and has 15% spell crit in gear. The first layout will have the 5% increased critical hit rate for destruction, while the second will not but will have DS instead. This scenario would be your classic Tier III/IV with good enchants. (~9001k bonus spell damage).
SM/R (2k Bolt, 15+5% Destro Crit): 2(4000)=8000 + 8(2000)=16000 = 24000
SM/DS (2k*1.15 Bolt, 15% Destro Crit) 1.5(3450)=5175 + 8.5(2300)=19550 = 24725
So a warlock of this virtual tier (III/IV) would improve their Shadow Bolt damage by slightly over 2.9322% by moving to SM/DS/Bane.
Reality check: if you have an appreciable amount of +spell hit (180200) necessary to make good use of Shadow Bolt and you're not kitted to the brim in the best of preSSC/BoE gear, this is likely your virtual tier. It's not a bad tier to be in either, this would be an 800900 DPS extendedterm, 11.1k short term DPS Warlock, well suited for raiding purposes.
Scenario #2: If we move the crit rate up to 25% (+10% of last example) for both parties, while maintaining the same +dmg we have a result of...
SM/R (2k Bolt, 25+5% Destro Crit): 3(4000)=12000 + 7(2000)=14000 = 26000
SM/DS (2k*1.15 Bolt, 25% Destro Crit): 2.5(3450)=8625 + 7.5(2300)=17250 = 25875
With 10% additional spell crit, the delta switched to SM/R leading, but not as much as what may have been perceived initially. The difference now is slightly over 0.4807% in Ruins favour. It took 10% spell crit added to the first scenario to raise Shadow Bolt damage on SM/Ruin by slightly over 3.4130%. This is assuming no spell hit or damage was lost in the process from the appreciably high rate of the first example.
Reality check: Near perfect spell hit with 25% crit (disincluding talents) and 1k bonus damage is not exceedingly easy to pull off. If you do, bravo.
This is without considering the options you're left with on utilising the remaining 10 talents offered by SM/Ruin.
For Affliction's utilisation of excess talents, the only general case raid beneficial use of SM/Ruin, would be 5/5 Contagion for its +5% bonus to Corruption and 3/3 Malediction for its +3% bonus to element damage.
For Destruction in regards to spending the extra 10, you really only have a better Immolate to show for 10 talents use.
For Demonology you could get a little more survivability.
These mediocre bonuses from 10 talents use has to compete with SM/DS/Bane's talent utilisation which includes the highest points of damage output available for all 3 trees.
In close, it was a nice Pre61Talent spec, but the old dog needs to die until it comes of use in the latter portions of the game (end of virtual Tier 5 or higher gear). This is excepting the Warlock or two in a raid that should have it simply to utilise the raid DPS output bonus of Malediction, while sacrificing some of their DPS.
Histasius 14:00, 6 October 2007 (UTC)
Merged stuff Edit
The calculation is wrong but the idea is interesting for noticing the importance of crit and hit. Probabilities are not additive and granted Hit chance and Crit chance are independant your formula should be :
Without Ruin : H * ( 1.5*C*A + (1C)*A ) With Ruin : H * ( 2*C*A + (1C)*A )
As far as I know Blizzard has not linked the hit and crit chance and thus they should be considered independant. Having more Hit chance results automatically in a dps increase without consideration of crit ratio.
I hope this article makes sense and it shows people the connection between this talent and two important game stats, namely crit chance and hit chance. Happy criting! Yvero 16:12, 8 December 2006 (EST)
 Some of the formulas could be expressed better, I think. Things like + (1H)*0 dont't really make sense, since they always evaluate to 0 (zero). Why even have that part if it's always zero? Should it be  (1H), instead? Fandyllic (talk) 5:06 PM PDT 13 Dec 2006
 I included that term for the sake of mathematical completeness. (1H) is the chance you will miss, and a miss does 0 damage. In expected value theorem, you're supposed to include all possibilities. As you pointed out, it evaluates to 0, and that is why the term doesn't appear in the later equations.Yvero 01:57, 14 December 2006 (EST)
It's also important to note that value of Ruin is directly related to the percentage of your damage that is caused by Destructionbased spells. When comparing UA to Ruin for example, consider having 40 points in Affliction and how that plays out. You will often DoT everything not CCed and look at the meters after the fact. Odds are your Destruction spell of choice will be shadowbolt as improved Shadow Bolt is nice for DoTs but your damage from Shadowbolts will most likely never raise above 50% or so. My personal numbers being 41/0/20 suggests that Shadowbolts are <30% of my damage in a run. As such, Ruin only affects 30% of my damage. In the end, I chose to spec out of Ruin and take UA just for this reason.
So, I think it's important to mention that you need to actually see a good chunk of your damage from Destruction for Ruin to be worth it. It doesn't even affect Seed of Corruption. ;) Terjekv 02:58, 14 February 2007 (EST)
Just noticed this section in Results:
 Scenario 1: If you have a 1% chance to miss, then you have an 99% chance to hit. Therefore, 1/99 is your chance to critically hit, when you hit.
with 5% chance to crit, shouldn't it instead be 5/99? I've edited it to reflect the changes, but revert if I'm wrong. :) Hemical 00:09, 24 March 2007 (EDT)
I have some doubts about the formula used. Indeed, according to Spell hit rating, 2 rolls are done: first to check wether the spell hits, and only if it does the game then rolls a second time to check if the spell crits. This means the damage formula is rather something like (with ruin) H*C*2*A + H*(1C)*A + (1H)*0, which then gives a percentage difference with/without ruin of C/(2+C). In other words, higher your crit chance, higher your dps increase. But the hit chance thus disappears from the formula, which actually makes sense as 2 different rolls are done concerning the hit chance and the crit chance Oizys 23:10, 29 August 2007 (UTC)