Reason why:
Poisons are one of the few weak points in T3nd0s masterpiece Skyrim Redone. There is no difference between them, they have some bugs/issues and are objectively unbalanced. Look at the paragraphs below to understand my thought process.

Overview:
This mod will give poisons more varied effects, better balance, will fix bugs and will give you the possibility for custom balance. Please understand that you must use the ReProccer to fully utilize this mod.

• Damage Health, Magicka and Stamina poisons come in 3 different ways that are suitable for different fighting styles and really feel different, one of these poisons uses a new mechanic that no other poison mod uses. Poisons are a bit stronger in general and should always feel useful but not overpowered.
• Damage Health poisons no longer dispell other poisons or harmful effects (fix from SkyRe)
• Damage Stamina/Magicka Regeneration poisons are now properly affected by the ReProccer (fix from SkyRe), for this reason they have been renamed to Impede Stamina/Magicka Regeneration
• Regenerate Health/Stamina/Magicka are now affected by the Fortify <string> in the ReProccer, for this reason they have been renamed to Fortify Health/Stamina/Magicka Recovery
• Ravage Stamina debuffs the target making it attack slower
• Ravage Magicka works like a "silence" from earlier TES games (but the enemies still taunt you)
  

The mod is free of scripts and can safely be installed and uninstalled in your current playthrough. Go ahead and test.

Detailed description:
The following explanations are valid for poisons that affect Health, Stamina (S) and Magicka (M). Ravage Stamina and Ravage Magicka have new experimental effects and these are open for discussion.
Please note that I will never speak about vanilla Skyrim, I will only cover changes from SkyRe.
There are 3 ways (effects) how a poison can deal damage to target:

Damage Health (S/M)
Lingering Damage Health (S/M)
Ravage Health

In SkyRe these effects all deal damage over time, which is a good thing - I think. A poison that burns your flesh like an acid, creeps through your veins and clouds your mind and drives you insane should be something that takes time - shouldn't it?
Then again these effects are very similar and because of a limitation of the ReProccer, the "Lingering Damage Health" effect is always superior to the other effects. If all poisons do the same and there is a first-best solution, why bother with the other poisons?

Immersive poisons for SkyRe changes the effects in the following way:

Damage Health (S/M)

• deals low damage over a duration of 5 seconds
• poisons can be stacked - if you hit your target with multiple poisons then all poisons take effect
  

This is a very straight forward poison, but poisons did not stack in vanilla SkyRe. So this is actually a big change.
Imagine this type of poison as some kind of acid - that burns flesh and bones. These poisons are really useful if you are dual-wielding two fast weapons, daggers maybe? Build your own style!

Lingering Damage Health (S/M)

• deals moderate damage over a duration of 10 seconds
• does not stack
  

Fire and forget! This type of poison might be suitable to weaken enemies before you finish them off with other means. It's just a standard poison that everyone could use.

Ravage Health

• deals low damage at the beginning and and then dynamically deals high damage over a total of 15 seconds
• does not stack
• uses the Taper mechanic that is present in the Construction Kit but wasn't used for anything but Fire Damage
  

This type of poison is fun to use. Yes, it is. If this poison is applied it will slowly creep through the veins of the victim and will kick in after a period of time and will then deal a high amount of damage.
In a melee battle this poison might be too slow but why not try a sniper build? Just make sure that your enemy won't reach you until the poison kicks in.

The general balance follows the idea that a full perk tree should feel worthwhile. A master alchemist will find his poisons nearly as powerful as the spells of a master of destruction magic are.


Ravage Stamina

• now reduces the attackspeed of the target by a flat 20%
• duration increases with Skill and perks (like Paralyze)
  

Stamina has an influence on fights, thanks to SkyRe - but you will rarely feel the difference between a bandit with full Stamina and an enemy that it is fully pumped out. I like the idea of giving fighting debuffs that make you feel a difference in combat.
Hits from enemies with slower attackspeed can be easier dodged, blocked (timed) and give you a bit more time to reevaluate the fight. Try - and give feedback!

Ravage Magicka

• effectively silencing the target, making it unable to cast spells for a short duration
• the duration scales with Alchemy skill and perks (like paralyze)
  

Unlike health which can be seen on the enemy health bar, magicka suffers from the issue that you have no idea how much magicka the enemy has left. You now have a fair window to get up and close to the mage before he will cast spells again. Try - and give feedback.

Impede Magicka/Stamina Regen - renamed from Damage [...]

• both types will now fully stop regeneration of Stamina and Magicka
• the duration scales with Alchemy Skill and perks
  

The concept of reducing Regeneration by 100% or even 150% was always a bit weird. It only seems appropriate if you have the formula in your mind. For gameplay reasons it is sufficient if the player knows if the target regenerates something or not. You know what? They don't regenerate. Make those mages dry and go in for the killing blow!

Reading? Ain't nobody got time for that! (Hollywood lost a real talent right there ...)

The video was made with Version 1.0 - some things have changed. The basic concept is the same.
It is not easy to demonstrate the changes in a video. Go ahead and test them in game and share your feedback with me.

Installation & Requirements:

Mods and programs you need:
T3nd0s Skyrim Redone
ReProccer - Automated SkyRe patch generator

Method 1 - NMM:

Please note that this method will overwrite your current stats.xml with a modified version of the most recent version from xathras/raulfins ReProccer patches. If you use their stats.xml, overwrite it with the .xml in my mod - I just changed the alchemy section.

1. Download the All-in-one version and install with NMM.

Load order: Place Immersive Poisons.esp after Skyre_Main.esp.

2. Run the ReProccer


Method 2 - manual:

The installation process consists of three steps. Download and activate the
mod (Immersive Poisons.esp), configure your ReProccer (stats.xml) and
run the ReProccer.

1.  Download the mod (ESP ONLY) and place it in your Skyrim/Data/ folder and activate the .esp
Load order: Place Immersive Poisons.esp after Skyre_Main.esp.

2.  Make a backup of your stats.xml file. You will find this file in your folder:
Steam\SteamApps\common\Skyrim\Data\SkyProc Patchers\T3nd0_ReProccer\ReProccer

2a. Download the "change_this_in_your_stats.xml" file and change the values or copy the part into your stats.xml.

3.  Run the ReProccer, make sure that you have "Patch Alchemy Ingredients" ticked.

If you are having trouble installing this, then you are maybe new to SkyRe and the ReProccer. In this case you can read my article about the ReProccer and how to change the stats.xml.

Compatibility:
The alchemy system of Skyrim is beautiful and ugly, simple in it's core but most parts are connected in a way that makes tweaking pretty hard. I'm happy to have found a way to change things without breaking others.
This mod does not touch a single ingredient. It will only change the effects and tell the ReProccer how to change the ingredients. Thus it is compatible with everything that does not change the effects of the poisons.
Ingredients that are added by other mods are compatible and will fully use the new effects. The balance of these ingredients though depends on how well or bad the mod author of his/her mod balanced them.

I went the extra mile for you and checked the following popular and wonderful mods that add ingredients:

83willows 101Bugs - overpowered - just check the comments at her mod
HarvestOverhaulCreatures - good - only Horker Blubber has an issue, the author will correct this in the next version
Wyrmstooth - good (as of 1.11)
Hunterborn - awesome (some ingredients are really strong, but if you mix a Dragon Heart into a potion it should be damn strong, shouldn't it?)
skyBirds - overpowered - even in vanilla Skyrim you can brew a 600 damage poison at level 1 and 20 Alchemy

Please understand that I love all of these mods because they are great.

This mod is also 100% compatible and tested with:
xathras/raulfins ReProccer patches
Radiant and Unique Potions and Poisons

Customization:
I tried to achieve a balance that is useful in all stages of the game and is neither too weak nor overpowered. If you don't agree - rejoice - you can help yourself.
You can adjust the power of your poisons by changing values in your stats.xml and then run the ReProccer. (No that can't be done within an MCM)

Example:
If you want to make your Damage Health poisons stronger and have a longer effect you can change these values:

<fMagnitudeFactorDamage>0.5</fMagnitudeFactorDamage> --- e.g. from 0.5 to 1 makes poisons respectively twice as strong
<iDurationBonusDamage>3</iDurationBonusDamage> --- e.g. from 3 to 8 makes poisons respectively twice as strong (5 seconds before - now 10 because of the inherent base duration of 2 seconds)

It is best if you read T3nd0s explanations on the ReProccer.

If you found an amazing balance, go ahead and share it with us in the comments.


FAQ:

Q: My poisons have really strange values like 0 seconds duration. Why?

A: If done correctly the ReProccer will change all ingredients. Make sure that every mod/patch = each .esp file that modifies ingredients is loaded before the ReProccer. Sometimes it's not obvious which mod has ingredients or not.
Being a SkyRe&ReProccer user you are already an advanced mod user. Go ahead - get TESVedit and check out your problem by yourself. Nobody can understand your load order better than you do, each Skyrim installation is unique and the person that can help the best is you.

Q: My potions/poisons are worth like 5000 septims and are super strong. Is your mod trash?

A: If you get crazy values then you most likely didn't run the ReProccer properly or the values of the ReProccer get overriden by a mod that is placed after the ReProccer. Damage Magicka Regen and Damage Stamina Rege (Impede) have issues in SkyRe and potions with a Giant's Toe have issues (high value) in vanilla Skyrim. My mod fixes both issues. Make sure you run the ReProccer.

Q: I turned on Papyrus logging and ...

A: My mod has zero scripts. It's just not possible. Also there is no better answer than:

"TURN OFF YOUR PAPYRUS LOGGING. THERE IS NEVER A REASON TO TURN IT ON IF YOU DON'T KNOW WHAT YOU ARE DOING. LEAVING IT ON MEANS THAT YOU DON'T." -Apollodown



Credits & Thanks:

T3nd0 for SkyRe - I wouldn't be playing Skyrim without this (until PerMa is coming out)
raulfin for his general wisdom and the stats.xml
xathra for his general awesomeness and the ReProccer patches
zaerosz for feedback and help with wordings
colector for testing and feedback