I was recently updating the Survival guides over at the Warcraft Hunters Union, and I saw that there was some disagreement about the optimal use of Explosive Trap in single target fights, when I realized there was a bit of disagreement in the hunter community. So I pulled up my spreadsheet, and downloaded the latest build of SimC, and set to work.
Here was my side of the argument: Arcane does more damage per execute (by execute, I mean each time you cast it) than Explosive Trap, so the only time Explosive Trap should be a higher priority is if Explosive Shot is about to come off CD, and you don't have enough focus to cast both an Arcane and an Explosive Shot. This method uses Exp. Trap as a sort of filler, when you need something to do for a GCD, but are a little short on focus. However, while I was thinking about focus in a general since, I wasn't looking closely enough about how the focus costs were affecting the entire fight.
Especially as we get into higher gear levels and Steady Focus becomes more and more productive than Thrill of the Hunt, we'll be seeing a lot more of those 40 focus Arcane Shots. That's a pretty huge focus cost, especially when compared to Explosive Trap (which is free). After tearing through some logs, and running some simulations on SimC, I've come to believe I was wrong before about Explosive Trap usage, and here's why:
While it is true, in any given instance, one Arcane Shot does more damage than the entire duration of one Explosive Trap, the amount of time you'll have to spend casting Focusing (or Cobra) Shots negates any DPS gain from casting Arcanes instead of Exp Traps.
For example, in a 7 minute fight (actually, about 100,000 seven minute (give or take 20 seconds) fights averaged together) if I only cast Explosive Trap as described above, I'll end up with about 9 Explosive Traps, and 137 Arcane Shots. If, instead, I cast Explosive Shot basically on CD (other than when it gets in the way of more important shots) I end up with about 34 Explosive Traps but only 125 Arcane Shots.
So, at the most basic level, I'm looking at a decision between 18 extra Arcane Shots (plus a few focusing shots), or 25 extra Exp. Traps. At 23596 per Arcane, 12584 per Focusing Shot (which is about 5763 per second), and 19110 per Exp Trap, we've got a fairly simple comparison.
Using Exp Trap selectively:
18*23596 + 5763*7 = 465069
Using Exp Trap on CD:
25*19110 = 477750
And that's what finally convinced me I had been wrong. Because you can't simply replace the GCD you would have used on the Exp. Trap with an Arcane Shot (since you'll have to make up for the focus cost of the Arcane with more Focusing Shots/Cobra Shots), using Explosive Trap on CD yields higher DPS.
The Lone Wolf Consideration
It's worth noting that these numbers are incredibly close together, and that's because Focusing Shot does some amount of damage. If you take Lone Wolf (which doesn't have as high of a DPS potential as Focusing Shot, but may be preferable in heavy movement fights), the damage of each Arcane goes up, but, we have to spend even more time casting Cobra Shots, since they don't return as much Focus as Focusing Shot. So in the end, we only end up getting 7 more Arcane Shots, compared to 24 more Explosive Traps from using them on CD; so we still end up DPS ahead by using Exp Trap as often as we can.