Btw just for the record these are the calculations I recently made on the regular Warrior forums. The results proved that fast weapons still beat slow weapons on damage even with deep wounds spec, as long as your rage resources are infinite. So for that matter Last Laugh should beat Calamity's Grasp at Patchwerk when it comes to both dps and tps output.
Calamitys grasp
445.38 weapon damage
2.6 weapon speed (before haste)
Last laugh
274.56 weapon damage
1.6 weapon speed
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1) Heroic strike damage over a 21 second timespan :
Formula : weapondamage + 495
Calculations:
a) Calamity's Grasp : 445.38x8 + 495x8 + 0.48x445.38x(8/3)x120%.
-The first part is weapondmg x number of heroic strikes
-The second is the bonus damage x number of heroic strikes
-The last part is deep wounds value x weapondmg x average crits x trauma/mangle modifier.
-As a crit value I took 33%, based on : 10% basic crit + 15% from talents + 5% rampage + agility totems should be around 33%.
-The same formula was applied for Last laugh, coming to results of :
Calamity's grasp : 3593+3960+684.10=
8237.1
Last laugh : 3569+6435+ 685.30=
10689
2) Bleed effects
A) Deep wounds procs on crits. Chances to proc during those 21seconds are based on crit%xheroic strikesx(Global cds in 21 seconds -1). The -1 stands for a gcd used on rend, which obviously can't proc deep wounds.
B) The question now is will the bleed dmg from those 13 gcds involving 1 rend + the extra devastate damage + calamity's dps stats undo that difference ?
-Small note: Calamity's grasp will use up only 96 rage on heroic strikes during that time VS 156 for last laugh, which also plays a role in overgeared situations, which is kind of where you want to test crazy stuff like this.
13 gcd's of which one (rend) can't proc deep wounds. Working with an estimation of 3 revenges, 4 shield slams, 4 devastates and a thunder clap. (3x0.18 + 4x 0.33 + 4x 0.18 + 1x 0.33)/12=~3 deep wound procs per 21 seconds.
I. 0.48x445.38x3= 1337.58 dmg for Calamity's Grasp
II. 0.48x445.38x3= 640.8 damage for Last Laugh
This portion of the calculations is in favor of Calamity's Grasp, simply due to higher max damage.
Difference after heroic strikes + deep wounds :
9574 VS 11329 so far.
Applying trauma modifier makes the difference slightly bigger : 1605.1 and 768.9 respectively.
Brings the scores to 9842.2 VS 11457.9 damage done with hs+deep wounds.
C)
Other factors are
C1) Rend
C2) Devastate
C3) Weapon stats
C1) rend
It's dmg consists of 5 subparts
I) main hand dmg (as displayed before)
II) attack power / 14 x weapon speed
III) base damage
IV) mob health
V) bleed modifier
Using "modest" stats I'll go out from a 4k average AP value for these calculations. Note that the chose AP value does not really matter when it comes to the difference between the outcomes.
Calamity's grasp :
Ia) 445.38
IIa) 4000/14x2.6= 742.86
IIIa) 315
IVa) 35% more dmg 1/4th of the time = 8.75% modifier
Va) Trauma = 20% modifier
Total 1)
1961.72 damage over the duration of rend.
Last Laugh :
Ib) 274.56
IIb) 4000/14x1.6=
IIIb) 315
IVb) 8.75%
Vb) 20%
Total 2)
1365.94 damage over the duration of rend
Again this helps Calamity's grasp close the gasp. However :
Subtotals :
11208.3 VS 12823.84 damage done with HS+DW+rend
C2) Devastate
Formula 50% weapondmg + 505
note that 505 comes from 5x101, and calamity's grasp will do significantly more damage on the first devastates. However during the course of a bossfight I think we can neglect the extra value of those "non-sundered devastates".
Dmg from 4 devastates : 2910.76 vs 2569.12
Again there's an advantage for Calamity's Grasp. Unfortunately the difference is yet again not so big due to the very small weapon damage factor in Devastate.
Subtotals :
14119.06 vs 15392.96
C3) Weaponstats
-Note: Calamity's grasp is actually not 2.60 speed due to haste on the item. and will benefit "more" from other haste buffs as windfury totem than last laugh will when it comes to heroic strikes per time unit. It also provides ~1.50% extra crit which benefits deep wounds.
-Inclduing haste enhancing buffs (non-improved windfury, uptime of 45 seconds per 5 minutes heroism, item stats) the average speed on both weapons is respectively 1.9515 and 1.2128.
This brings the number of heroics strikes to 10.761 and 17.315 in the previously used 21 second window.
damage contributed by heroic strike therefore is now :
I. Calamity's grasp :10.761x445.38 + (495x10.761) + 0.48x445.38x10.751 =
4792.7342+5326.695+ 2298.3746= 12418.004 damage
II.Last Laugh gives :
17.315x274.56 + 17.315x495 + 0.48x274.56x17.315 = 4754.0064+ 8570.925 + 2281.923 = 15606.8545 damage
-To make things a bit more clear again, here are the current subtotals after using the effective average weapon speed in a raid scenario with basic (non improved) windfury buff and heroism usage:
18299.964 for Calamity's grasp
20310.8145 for Last laugh
These values include HS+DW+DEV, enhanced with the most common raid setup's buffs.
D) Looking at the results :
Now how are we to interprete these results when it comes to the realistic scenarios ?
-In unlimited rage situations you'll probably do ~5.2% more damage with last laugh, since these abilities would do around half of total damage on single target encounters like patchwerk. (example taken from
Wow Web Stats).
-Calamity's grasp however becomes better as soon as heroic strike queue time drops under approximately 75%. (495 bonus dmg per extra heroic strike so ~4 heroic strikes needed to undo the dmg difference over 21 seconds).
Using Xavastraz's stats this would mean last laugh strongly beats calamity's grasp (5%-2.5%) at :
-Patchwerk
-Grand widow faerlina
-Malygos
-Satharion
-Gluth (Main tanking)
-Sapphiron
-Kel'thuzad
Last laugh marginally beats calamity's grasp (>2.5%)
-Anub'rekhan
-Maexxna
-Loatheb
-Grobbulus
Calamity's grasp is superior at :
-Noth the plaguebringer
-Heigan the unclean
-Gothik (because of the "trash" style encounter)
-4 horsemen
-Razuvious (add tanking, so of little importance)
-Gluth (add tanking)
-Thaddius (due to the massive DW % damage)
-About all trash encounters.
As final conclusions I think we can state the following :
1) Speccing deep wounds / impale is increasing your DPS regardless whether you use a slow or fast weapon. This isn't exactly proven with these calculations but I think it's commonly accepted by now.
2) Equal dps slow/fast weapons comparisons depend highly on the encounter and the fact whether or not you outgear it. However the more Crit and Haste % you have the closer the slow weapon will get on fights with infinite rage. You'll need unattainable values to actually beat the fast weapon though.
3) A "maxed out" tank will probably also find Calamity's grasp better at the 4 encounters where the difference is only marginally big. I'll personally parse my wws's next week in naxx25 if I get the chance and compare my own results. with that of the here used WWS.
4) In any encounter, Calamity's grasp proves to be the best dps performing weapon for tanks, with the exception of Last laugh on fights with infinite rage. No other weapon is assumed to come close enough to compete.
5) Final conclusion : Ideally you have both Calamity's grasp and Last Laugh, using them accordingly to the above specified encounters.
Hope this answers most questions. If you find any flaws in my maths or wish to ask addiontal questions, don't hesitate

.
Short note : With a fully melee-optimised raid (enh shaman, and note that heroism uptime isn't exactly 45 seconds out of 5 minutes, for example if a fight is 6 minutes, it's going to be 90 seconds out of 6 minutes or 25.7% uptime = 9% haste instead of 5.25%) and better offensive gear (crit and haste being the effective factors) the gap is going to get smaller and smaller, even at infinite rage fights. My guess is that with the factors I did not involve included you could say calamity's grasp is better as soon as the number of your white swings exceeds ~16-18% of the number of your heroic strikes.