I'm not sure what analysis you did, but the craft actions are independent. In essence if your success rate is 5% than you have a 95% degrade chance on every item, even if you make a million, and because the actions are independent you will have much lower than 5% on average.
I'm not sure you analysis of high levels should be applied to overcrafting; if overcrafting you gain 1.6% for every skill level you get closer to your action level- under your levels hypothesis this would give 1.6x the amount of points stated by the scrolls and craft window. However if the crafter's level is above their action level they only get 0.5% for every level above- this might explain you lower observations, or it was just random.
Finally, scrolls are not some rare thing. they are pretty easy to replace. and the 'minor' xp improvements can add up, because a boost of 8 or 10% might not get you your full action q but will increase the q of the majority of degrades.
I'm not sure you analysis of high levels should be applied to overcrafting; if overcrafting you gain 1.6% for every skill level you get closer to your action level- under your levels hypothesis this would give 1.6x the amount of points stated by the scrolls and craft window. However if the crafter's level is above their action level they only get 0.5% for every level above- this might explain you lower observations, or it was just random.
Finally, scrolls are not some rare thing. they are pretty easy to replace. and the 'minor' xp improvements can add up, because a boost of 8 or 10% might not get you your full action q but will increase the q of the majority of degrades.