Official stance on stacking buffs / debuffs?

[kaloel]

I've been looking for a long time for an adequate up to date answer for the question "what should stack?".

Spoiler:

Some SM abilities are too short in duration (Aug 28, 2015)
Magus armor self buff doesn't stacks with armor pot? (Oct 05, 2015)
Stacking: when is a tactic not a tactic? (Dec 28, 2015)
Potions- stacking elemental resists (Jan 14, 2016)
Buffs that stack? (Jan 24, 2016)
Buff Stacking Question: (Mar 02, 2016)
Stacking buffs (Sep 28, 2016)
[Ironbreaker] Oathing each other (Dec 15, 2016)
Stacking buff/ debuffs (May 08, 2017)
[Chosen] So many questions, where to begin. (Nov 30, 2017)
SM spirit debuff (Dec 03, 2017)
Buff/Debuff Tooltip Clarification (Jul 29, 2018)
Dok heal debuff vs wp one. (Oct 01, 2020)
Also about 100 reports on the bugtracker about "stacking"

What I've generally found as an answer:
Movement speed, wounds and heal DEbuffs do not stack; at all. (heal buffs do stack)
Nothing stacks with itself. (6x Focused Mending is still 15%)
For everything else:

[MAX (Ability / Potion) ]
+
[MAX (Morale)]
+
[SUM (Tactic)]
+
[SUM (Career Mechanic, Heaven's Blade, Daemonic Armor, Flak Jacket)]

The last part seems to be exceptions, for skills that would be useless if they didn't stack, thus they were allowed to stack with everything.
Is there a list containing all of these intentional exceptions?
This seems to apply to buffs and debuffs in the same way. BUT:
What if a tactic changes an ability?
E.g. Big Brawlin' (BO), Focused Mending (KotBS), there are about a dozen of these tactics per side. Does this count as a tactic, since without it it would not have the effect OR does it count as ability, as it is still an ability that applies it?
Based on testing these tactics are split about 50/50, so there is no telling what is intentional, and it is really annoying to test all these by myself...

It would be really useful to have an "official" response, to allow us to make more meaningful bug reports. Because right now its anyone's guess what the intended exceptions are, and what the correct stacking rules are...
PS: Would be great to have something in the wiki about this. That can be updated if it changes, so we don't get the monthly 10 page question thread "Does a stack with b?".

[Manatikik]

You can only have one buff of the same kind per source (ability, tactic, morale, career).

Ability buffs are anything a skill gives you, potion, or item proc; so you could have a BS potion, RP/Z buff, and a Conqueror BS proc on SW/SH/Eng but only the highest value will count. Things like RP/Z stat buff and SM/BO stat steal count as ability and not career.

So on destro Cutting Claw and Wot Armor armor debuff don’t stack but Cutting Claw and Demo Strike/Zealot M1 do stack to significantly lower armor values.

Certain tactics that add a debuff to something add a secondary Tactic debuff and some just add it to the skill so it counts as ability not tactic source (examples on order are Overpowering Swing on Knight or Vindication on WH).

There are also several outliers that do not follow this rule set due to balance such as Wrist Slash tactic on SW does not stack with other sources on the debuff portion (but it does stack on the buff portion).

It’s sometimes rare to find a way to meaningfully stack all three sources together due to this (or good example is SW with crit stacking; you can get 5% from a link, 20% from a tactic, and 12% from Sov proc).

[kaloel]

You can only have one buff of the same kind per source (ability, tactic, morale, career).

Ability buffs are anything a skill gives you, potion, or item proc; so you could have a BS potion, RP/Z buff, and a Conqueror BS proc on SW/SH/Eng but only the highest value will count. Things like RP/Z stat buff and SM/BO stat steal count as ability and not career.

It’s sometimes rare to find a way to meaningfully stack all three sources together due to this (or good example is SW with crit stacking; you can get 5% from a link, 20% from a tactic, and 12% from Sov proc).

Shouldn't the liniment crit (potion) not stack with the 12% sov proc, based on your explanation of what should stack? Both should be counted as abilities, right?

[Manatikik]

You can only have one buff of the same kind per source (ability, tactic, morale, career).

Ability buffs are anything a skill gives you, potion, or item proc; so you could have a BS potion, RP/Z buff, and a Conqueror BS proc on SW/SH/Eng but only the highest value will count. Things like RP/Z stat buff and SM/BO stat steal count as ability and not career.

It’s sometimes rare to find a way to meaningfully stack all three sources together due to this (or good example is SW with crit stacking; you can get 5% from a link, 20% from a tactic, and 12% from Sov proc).

Shouldn't the liniment crit (potion) not stack with the 12% sov proc, based on your explanation of what should stack? Both should be counted as abilities, right?

Yes, I misspoke. What I was meaning to say was the 5% from skirm stance stacks with the other two sources (the BS from the lini stacks with BS with Scout BS and MA+IA).

[kaloel]

Okay, so the stance does not count as an ability, but as a career mechanic, right? (Because abilities would not stack with potions/abilities, so its not an ability. And it obviously is not a morale or tactic.)