I've been trying to dig a bit deeper into a good understanding of crafting and ended up with some questions and some (possible) feedback. I apologize if any of these questions have been answered before, I couldn't find any clear sources on it.
First of all, here are the assumptions I'm working with based on my ingame experimentation (apologies for the length):
Base crafting stats
I believe the three different crafting stats have a baseline value that holds true for any character that has zero skillpoints and zero stats.
Assembly skill: 4.00
Experimentation skill: 0.00
Experimentation points: 1.80
Character stat influences
Assembly skill is affected by +strength.
1 str = 0.0335 assembly skill
Experimentation skill is affected by +intellect
1 int = 0.05 experimentation skill
Experimentation points are also affected by +strength
1 str = 0.0135 experimentation points
This seems to hold true for other crafting professions as well (based on my limited testing) although the stat affecting the skill may differ (e.g. dexterity for leatherworking)
Max + crafting skill from skill trees
The basic crafting track gives a maximum of:
+5 Assembly skill
+0 Experimentation skill
+0 Experimentation points
The blacksmithing crafting track gives a maximum of:
+75 Assembly skill
+65 Experimentation skill
+8 Experimentation points
(+15 speed, but not relevant for this topic)
The optional racial track (e.g. 'mankind' or 'wood elf') gives a maximum of:
+10 assembly skill
+5 experimentation skill
+0 experimentation points
The crafting skill caps are all 100, except for experimentation points which caps out at 20. As I have not obtained a crafted vessel yet, I'm unaware of this influences those caps (apart from having higher character stats which would push the skills themselves higher).
Crafting leadership track
I do not have this skill unlocked, but according to the tooltips the skills only grant bonus points for Basic crafting, I'm assuming it does not (currently) affect specialist crafting skills.
Item difficulty and crafting success
It appears that the base chance to craft an item (before skills) is simply 100% - the item difficulty. Then the skill is added back on. So for example a 'mail coif' which has a difficulty of 35 for a character with 10.00 blacksmithing assembly skill would be 100-35+10 = 75% chance to craft.
I have not observed an increase in difficulty using a higher quality material (e.g. 'uncommon').
There seems to be a hard success chance cap of 97%.
I have not been able to test if 'optional' items (e.g. 'hunger shards') add to difficulty, as I don't have any.
The highest difficulty blacksmith recipe I've seen has a difficulty of 35. There are only a few recipes I'm missing currently (from the 'Research Mastery' pips), they might have a bit more difficulty but I don't know right now.
Experimentation succes and pips
For experimentation pips it seems the number is always rounded down. Having 2.8 pips on the sheet I get 2 pips.
I am unclear on how Experimentation success skill affects the success rate. Crafting a difficulty 5 item with 14 experimentation skill while having two pips results with both pips equalling 50% risk. Another item with difficulty 25 while having 11 experimentation skill results in having the same 50/50 ratio. I'm unclear on how this works.
Now that my assumptions about the inner workings are out of the way on to the questions.
1. The Assembly skill cap is 100. Even when I combine the points in the basic, blacksmith and racial track I end up with 90 assembly skill requiring another 10 skill, which equals 299 strength. (in 5.7 it seems the base cap for a stat will be 250 with racial bonuses affected this positively or negatively). However, with the way the success chance seems to work, what's the point in investing all these points? Crafting a 35 difficulty item and assuming the 97% chance hard cap I would only ever require a total of 32 assembly skill to hit the cap. Do points above that help me at all?
2. Should pips be always rounded down? It forces you to either 'go big or go home'?
3. How does experimentation success chance work actually work?
4. Is there anything that affects the base difficulty of an item? Is there an intention for item rarity to affect it?
5. Unrelated bonus question: Why are two handed weapon recipes behind the one handed recipes? I feel they should be lateral moves as they aren't different in 'strength' but simply dependant on which class can wield what.