I've recently finished work on a poison damage calculator for Diablo II. After a few revisions, I'm now reasonably confident that it's accurate (or at least, I've corrected all the errors that I've been able to identify myself).
It covers poison damage from both skills and items (and combinations thereof) with +% to Poison Skill Damage, -% to Enemy Poison Resistance, Lower Resist and the target's Poison Resist % and Poison Length Reduced by %. Unfortunately it doesn't really cover duelling, but it can still be used to help calculate poison damage to your opponents.
It's a Microsoft Excel worksheet. I've protected all the cells that don't need any input, and those that do require input are light grey or green. I've made some attempt to make it idiot-proof, but my expertise is limited (e.g. no list or check boxes) and it still operates mostly on the 'garbage in, garbage out' principle. It should (hopefully) be pretty self-explanatory and doesn't require in-depth knowledge (if you know that you can't equip two helms or socket a dagger with 6 perfect Emeralds, you shouldn't have any problems).
If you do have any problems, let me know and I'll see what I can do.
Here are some links which go into more detail about how poison works:
UPDATE 24 MARCH 2010 I've updated the calculator to take account of Poison Nova's increased damage in 1.13.
UPDATE 30 SEPTEMBER 2012 I've updated the calculator to correct poison length calculation for Multiple Shot, Strafe, Blade Sentinel, Blade Fury and Blade Shield. However, I experienced an error when attempting to upload the new version and unfortunately I had already deleted the old version. The updated calculator can be downloaded by clicking on the following link:
The row for Venom is only for when it's cast, so only skill level and +% to Poison Skill Damage are applied at that stage. You'll notice that when you enter values for Venom, its rate and length are added to all applicable skills, and then Lower Resist and -% to Enemy Poison Resistance (and +% PSD, where applicable) are applied to those skills.
Melee covers all melee attacks and Ranged covers all ranged attacks, with the exception of any poison skills and those that apply a fraction of weapon damage (with the exception of Lightning Bolt, which only applies lightning damage from converted physical damage and items).
Simply amazing. Good work! I've been looking for something like this for a long time. I've made a few poison nova necros the past few ladders and always wondered what the best gear setup was. After doing a few side by side comparisons, I'm happy to see I was on the right track. Thanks so much.
The number of skill points invested in synergy skills should be entered in the synergy column. For example, if you're calculating Poison Dagger damage and you have 15 points in Poison Explosion and 10 points in Poison Nova, you should enter 25 (15+10).
Although you can enter any number you like, I'm imposed conditions on the calculation so that invalid entries won't be considered: entering negative numbers will have the same result as zero, and higher than maximum synergy points will have the same result as maximum synergy points (e.g. entering 400 for Poison Dagger has the same result as 40, or 20 points each in Poison Explosion and Nova).
I tested to confirm exactly how poison damage is calculated, and I'm personally satisfied that the calculator is as accurate as it can be: unfortunately, at this stage it's unlikely that someone will take the time to confirm this independently. :\
The Calculating Poison Damage thread should answer your questions on things like bit rate (and includes a link to an archived copy of the Tao of Poison).
Ive returned to D2 after a decently long break, and after spending a few hours looking over the net trying to get caught up to speed this thread (and its related guides) have answered 99% of the questions I had. I am so glad I found this thread, and I want to extend my thanks for the hours of work put in to produce such a professional quality result. What more can I really say, thank you very much!
This chart appears to quite sound. I have a question however...
After the Lower Resist cells, there is a PR% and a PLR%--I assume one of them has to do with psn length?
Could somebody smarter than I, please clarify?