Couple Notes on the Marks T18 2pc Set Bonus

In one of the PTR builds released last week, Blizzard fixed an issue where the MM 2 piece set bonus (4 seconds of Rapid Fire) was not applying Careful Aim.  Now that it is correctly increasing the Crit chance of Aimed Shots, someone in the SimC IRC asked what happened if the 2pc Rapid Fire happened at the same time as our normal Rapid Fire (wondering if the Haste effect stacked).  After looking through dozens and dozens of MM logs from Hellfire Citadel, I was unable to find any examples of the two buffs occurring at the same time, but I did finally find an example (twice in one fight, oddly enough) of one of the buffs cutting off the the other.  After searching through more logs, I (and Jademcian and Lokrick, who do the real work on SimC) feel fairly confident that this is how the 2pc Rapid Fire works: when you cast or proc Rapid Fire while Rapid Fire is already active, whichever has the longer duration will replace the other.

That is to say, if you have, for example, proc'ed the 2pc Rapid Fire at second 0, then at second 2 you cast your normal Rapid Fire, your normal Rapid Fire will cancel out the 2pc proc, and you'll have a fresh 15 seconds of Rapid Fire.  If, on the other hand, you've already cast Rapid Fire, on what we'll again call second 0, and on second 12 you cast a Chim Shot which proc's the 2pc Rapid Fire, it will cancel out your normal RF and give you 4 new seconds of Rapid Fire (because, 4 seconds of the 2pc RF is longer than the 3 seconds you'd had left of the normal RF).  And finally, if you cast your normal Rapid Fire at second 0, and then cast a Chim Shot which proc's the 2pc Rapid Fire at second 8, nothing will happen, because the 7 seconds of normal RF left is longer than the 4 seconds of 2pc RF would be.

Marksmanship 2 piece set bonus Rapid Fire tier 18

Taking Advantage of the 2 Piece

Now that the 2pc set bonus is applying Careful Aim, we'll have to make sure we're taking advantage of that extra crit as much as possible.  As has already been mentioned on this blog, to do this we'll have to pay a bit closer attention to our focus pooling.  We want to be at nearly full focus when Chim Shot comes off CD, just in case we proc Rapid Fire, that way we can quickly spam out several Aimed Shots crits.

The other thing to pay attention to is when the 2 piece is proc'ing and your normal Rapid Fire is about to come off CD. In the graph shown above, this hunter cast Rapid Fire while his 2 pc Rapid Fire was already Proc'ed, thus costing him about 3 seconds of Rapid Fire.  Unless you're just very good at always looking at your buffs icons, this means you'll definitely want a Weak Aura or Tellmewhen icon set up to let you know when the 2 piece has proc'ed.

Of course, if the 2 piece proc's when you've already cast your normal Rapid Fire, there's not much you can do about it. As by far your most damaging shot, you do not want to delay Chim Shot for the 15 seconds of Rapid Fire.  There are times when Chim Shot comes off CD during the last few seconds of Rapid Fire; so I thought it might be worth looking into whether or not it's worth it to delay Chim Shot for a few seconds, just in case you proc'ed the 2 piece, which I'll get to in just a moment. First we need to understand a bit more about the 2 piece proc's during Rapid Fire.

2 Piece Proc's During Rapid Fire

As I've mentioned before, we're not going to see a lot of proc's from the 2 piece set bonus. Let's say, for example, you're a heroic raider in pretty good gear with a 37.5% Crit chance. That means you have a 15% chance to proc the 2 piece every time you cast Chim Shot (0.375*0.4=0.15).  That means you're looking at getting roughly 1 proc every 60 seconds (9/0.15=60, and yes, I used 37.5% crit so that it would be 1 proc per minute).  

Since Chim Shot has a 9 second CD, if you use both Chim Shot and Rapid Fire on CD, you'll end up casting about 1.667 Chim Shots during Rapid Fire (on average, of course).   That means your chance to proc a 2pc Rapid Fire during your normal Rapid Fire is about 23.73% (that is: 1-(1-0.15)^1.667 = 0.23732).  

A more useful way to think about that, perhaps, is that you're going to get about 12.5% of your 2 piece Rapid Fires during your normal Rapid Fire.  So instead of the 6.667% up-time we'd get if we didn't cast any normal rapid fires (4sec/60sec), we can only expect to see about 5.833% up-time in this example.

Delaying Chim Shot during Rapid Fire

Back to our original question "is it worth delaying Chim Shot for the last few seconds of Rapid Fire?" We only need a bit more information.  In 700 ilvl gear on the PTR, my AiS hits average 31766.6 damage, with crits averaging 78818.8 damage.  My Chim Shot, averages (hits and crits together) 106976.7 damage.  If we only look at the extra damage from Careful Aim (there's also some extra damage from haste, but it's negligible enough that we'll ignore it for now), 4 seconds of Rapid Fire, if we could manage to get lucky with TotH proc's, and spammed 4 Aimed Shots, we'd get an extra 188,208.8 damage (compared to using those same GCDs for Aimed Shots without Careful Aim).  However, we'll only get that extra damage 15% of the time (since we have a 15% chance to proc the 2pc Rapid Fire, as noted above).  That means our expected value for delaying Chim Shot 4 seconds is only 28,231.3.  

Since if you delay Chim Shot for 9 seconds you've lost the entire damage of one Chim Shot, it's fair to say delaying it 4 seconds will on average cost you four nineths of a Chim Shot, which is 47545.2 damage.  We can run a similar comparison if we only had to delay it any number of seconds, which will look like this:

Gained from 2pc RFLost delaying Chim Shot
1 sec7057.8311886.3
2 sec14115.6623772.6
3 sec21173.4935658.9
4 sec28231.3247545.2

In all of these situations, we'll, on average, lose more by delaying Chim Shot than we'll gain by getting extra up-time on Rapid Fire.  


  1. Pool up focus before every Chim Shot so you can spam Aimed Shots if the 2pc Rapid Fire proc's.
  2. If the 2pc Rapid Fire has proc'ed, do not cast your normal Rapid Fire until the 2pc finishes. 
  3. If you've already cast your normal Rapid Fire, continue using Chim Shot on CD as you normally would, as it does too much damage to ever ignore/delay.  


  1. Good analysis. Doesn't change my feelings about how garbage this 2pc bonus is though. Just making it extend RF's duration if you accidentally overwirte the 2pc or if 2pc procs during your RF would be a huge QOL improvement.

    As is, this is among the worst set bonuses I can remember having in the last several years.

    1. I definitely agree. There's very little to gain on this one. Even if the 2pc extended the normal RF, it happens so rarely that we wouldn't get much DPS out of it. I guess they're just banking on hunters enjoying instant Aimed Shots enough that they won't mind that there isn't a 2pc set bonus...

    2. I had hoped that when Blizzard asked for T18 set bonus feedback they'd see the many comments pointing out how lackluster and hard to use this bonus is and that it would be changed for the better. Of course, I also hoped Survival would be made viable so I'm incredibly perplexed as to what Blizzard is doing with the Hunter.

      Myself, I probably will stick with BM until I get T18 4-set and then might be switching to MM for better single-target dps.

  2. They should have just had it add 4 seconds to any currently active rapid fire if there was one running. I'd love to ask them the reasoning behind this decision but I am afraid their answer, however they said it, would come out in my mind as "we didn't do it that way because that way makes to much sense."

    I do wonder why they do it this way, it just adds more useless RNG to numbers. It is entirely possible although extremely unlikely that you could end up losing a bunch of the bonus rapid fires. When you are someone like me, who has notoriously bad luck, this type of design is not appealing even in the slightest. Oh how I wish for the days where your numbers were dictated completely based on skill and not luck.

    1. You know what I just realized this morning, is I totally left out the Careful Aim you get when your target is at >80% HP. So really we're going to be wasting even more of these than I indicated. I mean, we'll still get the haste benefit from them, but 4 seconds of 40% brings my autoshot from every ~2.6 seconds to every ~1.86 seconds, so I'd get 1 extra autoshot, and 7.36 extra focus... yeah, that's basically nothing. I should probably add that into this blog post somewhere...

      Perhaps the least impactful set bonus ever.