So, there has been a lot of debate on which of these feats is better. I, apparently like to torture myself. So, I went through and did some testing, and did the maths, and here is what I came up with:

I took off everything that altered my stats in preview, all boons, all companions except Erinyes of Belial (unsummoned), and I basically respecced without putting points into anything except choosing Master infiltrator.

**REMEMBER THIS EQUATION: Damage = Base * (1+ Total Critical Severity+Total Combat Advantage)**

I used Dazing Strike and got my base damage, my crit damage (non stealth), and stealthed damage.

Power: 18,381

Crit severity: 85%

Combat advantage = attribute bonus + stat bonus + base = 2% + 6.9%+ 15% = 23.9%

TEST HITS:

Base (includes power bonus): 2490

Crit (crit severity): 4606

Stealth (Crit + Combat advantage): 5200

So this checks out with our equation:

For just a critical strike Damage = Base *(1+(.85)) = 4606.5

For stealth hits we add in Combat Advantage= 2490 * (1+.85 + .2388) = 5201.6

I kind of expect it to be a point or two off as we are probable rounding some of the numbers that Neverwinter doesn’t, or the numbers Neverwinter gives us are rounded from the numbers it uses to actually come up with the damage.

**GRIM PLEASURE**:

I took heroic feats that don’t affect damage: Action Advantage, Swift Footwork, Improved Cunning Sneak, etc.

I took ONLY Grim Pleasure

I then attacked with cloud of steel until I hit a crit, and hit using dazing strike without critting, a hit critting, and a stealth hit.

My power went to 19,300 after hitting my first crit.

**The first critical hit you do does NOT get the buff.**

TEST HITS:

Base hit: 2529

Crit: 4679

Stealth: 5282

This checks out with our previous numbers and equations:

2529/2490 = 1.0157 or **1.57%** increase in damage.

This checks out this way, as well: (1+(19300/40000))/(1+(18381/40000))=1.0157 or 1.57%

The rest is pretty straightforward plugging in our numbers:

Crit damage = 2529 * (1+.85) = 4678.65

Stealth damage = 2529 * (1+.85+.239) = 5283.08

I added my companion with bondings and brutality rings and the change in power from Grim pleasure did not change so **it is ONLY your BASE power**.

ARTERIAL CUT:

I respecced using the same non effecting heroic feats and took only Arterial Cut.

Power: 18,381

TEST HITS:

Base: 2490

Crit: 4606

Stealth: 5574

The Base and Crit are identical to the test I did without feats, so that checks out, as expected.

The stealth should be 2490 * (1 + 1 + .239) = 5575.1

So, Arterial Cut performs as expected with an added 15% crit severity to damage delt while you are in stealth.

In this example, with these stats, hits from stealth do 5574/5200 = 1.0719 or 7.2% more damage with arterial cut. However, you have to keep in mind that that extra damage only counts in damage from stealth. If we are generous and say we do 40% of our damage from stealth, .4*.0719 = .02876 or 2.9% added damage with this feat. Compared with Grim Pleasure which we’ve already established, with these stats, gives us about a 1.57% increase in damage, it’s seems Arterial Cut is the clear choice.

However, here is where it gets complicated (I know right?):

The effectiveness of Arterial Cut goes way down the more Crit severity and combat advantage you get. For example, if you had 150% Crit Severity (pretty common end game) and 40% Combat Advantage Bonus (also fairly common), using my base damage stats from above, without Arterial Cut, you get stealthed damage of:

2490 * (1+1.5+.4)= 7221

Add in the 15% from arterial cut:

2490* (1+1.5+.15+.4)= 7594.5 or 7595 rounded

7595/7221= 1.052or 5.2% increase in stealth using Arterial Cut. Say you do 40% of your damage from stealth (which is pretty generous IMO), that gives it an effective damage increase of 5.2% * 40% = 2.1% extra damage.

BUT, as your base power goes up, Grim Pleasure gets better. To find out at what point our power needs to get to in order for Grim Pleasure to be better than Arterial Cut, we gotta go back to our maths (again):

We want to find the point at which our power increase with Grim Pleasure reaches 2.1%. Let’s go back to this equation:

(1+(power1/40000))/(1+(power2/40000)) = percentage difference in damage that power 1 is over power 2

(1+(power1/40000))/(1+(power2/40000)) = 1.021

Then if we take x as our needed power and make the first power x * (grim pleasure buff), our equation looks like this:

(1+(x*1.05)/40000))/(1+(x/40000) = 1.021

Solve for x (rounding) = 28,966 base power needed to out perform Arterial Cut.

READ THIS PART IF YOU SKIPPED TO THE END:

So, here is the bottom line, fellow TRs: The Big assumption is the amount of damage you do from stealth. For me, I feel like I am being generous at assuming 40%. But that number is going to be different for everyone depending on their build. And, you don’t have to go much higher than 40% to make it impossible for Grim Pleasure to keep up. For example, if you do 45% of your damage from stealth, the amount of base power you need to pass up Arterial Cut with Grim Pleasure jumps to 36,482. But, if you do 35% damage from stealth you’ll only need 22,500 base power.

Keep in mind the variables: your base power, your crit severity, your combat advantage, and the amount of damage you do from stealth.

Also, realize that the difference between the two feats is, less than 1.5% damage.

Yeah, I just wrote a friggan dissertation over 1.5% difference.

Thank you to @chemodan007, @rustlord, and @micky1p00 over on the official forums for helping me out on this!

Never ever try to do this kind of work without coffee.