Today we take up the DA modifier, or written in full, the Double Attack modifier. Double Attack Percentage ranges from 0 to 100%. Double attacks are not called out in the logs as such, so it is difficult to gather data on them as such. In a run of 267 melee atttacks versus basilisks in Bonemire, I had one attack that might have been a double attack. Given that my Double Attack percentage is 1%, this is a reasonable outcome, in fact, there’s a 7% chance that I would get no double attacks whatsoever in a run of 267 autoattacks.

So, I’m going to assume the following things about double attacks:

- Double attack chance is rolled on an attack that hits. Misses are ignored.
- If the double attack chance succeeds, it means a second attack has hit, no “to-hit” roll applies.
- Damage for the second hit is calculated normally, subject to DPS mod, STR, critical hits, and so on.
- Second hits will not trigger procs.
- Only autoattack hits are affected.

Ok, I’ve made a few charts showing tradeoffs between DA and Attack Speed (haste). The first thing to notice is that X% DA has the same effect on DPS as X% haste, assuming that the other modifier is zero. Put another way, swapping your DA and attack speed modifier will leave your DPS unchanged.

The second thing to notice is that the same 50 points of modifier gives the largest gain when spread equally between haste and DA. Which gives us an important rule of thumb: increases in the smaller modifier are worth more, even if you figure in diminishing returns.

The next table considers a character with 70% haste and 5% double attack. This isn’t too unreasonable for someone who has the haste cloak and is grouped with an illusionist or troubador. We then look at the effect of adding between one and five points to either haste or DA.

We see that adding to DA increases output DPS by more than adding the same amount to haste in this situation. And that’s not accounting for the fact that haste is on diminishing returns. I used the percentage figures in the chart, but at that level of haste, one point of Attack Speed is going to be worth less than 1% haste, perhaps only .75%.

There’s nothing special about the nature of haste or DA that makes this so, if someone had 70% DA and 5% haste, then adding to haste would have the larger effect. In fact, we could substitute in Melee crit chance and the effects would be similar. The big problem with modeling Melee Critical is that the magnitude of its effect on DPS depends on the damage spread of the weapon used, because of the critical damage minimum value. Melee Critical chance affects combat arts, too. So we’ll leave the tradeoffs for another day.