Yes, quality while crafting is confusing at start, but as soon as the clouds are scattered the sun shines
In this thread we have merged a few different topics now, but yes, they are interleaved, or vowen together, in the crafting. I will take it note by note:
Meeting a stat only once only makes sense if it is possible. Most often it is not possible, almost never in the more complex items. Furthermore, it only makes sense if the resource meeting that stat is better than any other other resource for the same stat. Lubricating Oil tends to be a great resource when a schematic slot calls for Chemical and the other resources are great.
It is the each one resource slot in the schematic that sets the possible cap for that slot, not the resource you actually are using. If a slot calls for Steel and CD is one of the stats called for, then the cap for CD is set to 650, no matter which type of steel you use. If you use a so called JTL* Steel (Crystallized Bicorbantium Steel or Hardened Arveshium Steel) which has no cap for CD you will easily find a steel that gives 100% on CD for that slot. If you on the other hand use Rhodium Steel you can never ever get CD for that slot better than 13% since that steel has a cap on CD of 85, but the slot has a cap of 650.
Only if a slot calls for a particular resource class it is that resource class' cap that is considered, otherwise it is always the cap of the more generic resource class that is called for that is used in the formula, no matter what sub-class you use.
Finally, while we tend to say it is the average of a stat that is used, the correct term should rather be the "weighted average" since how much of each resource is used is also considered. Using 100 units of a steel and 25 units of a chemical gives the steel 100/125 vs. 25/125 == 4/5 vs. 1/5 weight. That is, steel in this example is 4 times as important.
All of this combined makes crafting so much fun, it is not just to take some gold ore, silver ore, or whatever, and melt it and get some stuff that always is the same and that always will produce the same weapons, as many other games have it with crafting. SWG calls for some thinking and each crafter can combine resources in his/her fashion. But yes, the learning curve is sometimes steep and that is the reason I advise against speed-grinding.
* JTL "resource" since these resource classes were introduced with the JTL expansion in 2004. To my understanding none of them are capped.
/Zimoon