It's pretty easily actually, just not "intuitive".

- Poison dmg is reported as "total Dmg" over "time"
- This is UNRELATED to how dmg is REALLY calculated, therein lies the confusion.
- Poison dmg from an item is based on its "duration" (the 'over' time above) and its RATE. The rate is the dmg it does divided by the time. For example 6 points over 3 seconds is 2 pts/sec for 3 sec.
- Multiple items/gems/bonuses in one attack *do stack*, by adding BOTH rates and duration
- Multiple hits one after the other do NOT stack. Sometimes they are utterly ignored, other times they overwrite.

Let's look at those last two points
On a SINGLE hit, add up the rates and durations of all items/skills involved. Dagger of Venom doing 6 dmg over 3 sec is 2.0 pts/sec for 3. Snakecord might add 6 over 2 seconds, that's 2.0-4.0 pts/sec for 2.0 sec (I'm making the numbers up, not looking up unique attibutes). Add in Venom Ward, something like 9 pts over 3 secs - that's 3.0 pts/sec for 3.
Add rates: 2.0+3.0+3.0 = 8.0 pts/sec
Add durations: 3+2+3 = 8 seconds.
Total dmg: 8/sec * 8 sec = 64 points If you were to incorrectly add the "dmg done" (6+6+9) you would get a wrong, low, number (21 pts). So you're getting about triple what you expect.

If you use a Kris with two emeralds, EACH gems adds its rate and duration individually. If you use Poison dagger skill, things really get interesting. There the duration can go way up. So using Snakecord and Venom Ward and ring of blight can add up to massive dmg, but over a very loooong time.

Mixing a high rate item (item of pestilence) with a long duration item/effect (PD skill) does wonders.

Now, if that's true, why does poison suck??? Three reasons, first off, your sorceress partner will FO the dying monsters in 0.7 seconds, not wait 45 seconds for the monster to keel over. Second, monster poison resistance cuts BOTH rate and duration. So if it has 50% resistance, that's 50% rate and 50% duration for 1/4 total dmg taken. Finally, subsequent hits do NOT stack...

Multiple Hits...
When a monster is first struck with poison, the program keeps track of just TWO numbers - the rate and duration. When a monster already poisoned is struck with another poison attack, the RATE of the new attack is compared with the rate of the existing poison, and if it is lower, the new attack's poison is IGNORED. If the new rate is higher, BOTH the rate and duration are replaced. So if a monster is in the process of taking 2.9pts/sec for 45 seconds and is hit by 3.0 pts/sec for 2 seconds, total damage will DROP from almost 90 to 6 pts.

Do you bother hitting multiple times then? Well, there is some small advantage. First, the numbers are not constants but ranges, so if the rate is 2.0-8.0/sec, the average rate is 5.0. This is the 50% percentile. With multiple hits, the "expected value" changes from the 50th percentile to 75, to 87.5, to 93.75...
So the damage the monster will take will not quite double if you pound him repeatedly (over the time it is green) When an "higher rate" strike does kick in, it also has the advantage of resetting the duration (well, setting the duration value to the duration of the new attack)

Clear as mud? Bottom line: yes, a max-PD + wpn of pestilence (or dual emerald kris) + Snakecord + Venom Ward + 2 rings of blight + amu of blight leads to total dmg, of somewhere between 1000 and 2000 ! Alas, it will take over a minute to apply that dmg :P (Not sure if the listed dmg is correct. It used to be hopelessly wrong, maybe 1.05 fixed that)

Charis