MonsieurVerde, you are correct in some of what you said. SE wrote the help page you are talking about in October 2010, and if you played since the beginning, you would know that Crafting has been changed a few times. In the very beginning it was so easy to do anything, it was more what tool you had in your hand vs what you were crafting. Since they patched it I believe in the November patch, its a little different.

This is my Theory (What affects success in ranking order most important to least important)...

1) Your Rank vs Item Rank (You can do up to 9 ranks below to synth an item, granted 9 ranks below your success sucks, Each rank closer you increase that success rate)
2) Main Hand/Off Hand Vs Items Preferred Tool (What I mean by this, is its easier to make an item that you produce more quantity than it is to make an item that produces HQs, this is IF your control/craftmanship and magic craftsmanship are the same for both, which they never really are)
3) Moon Phase (Some moon phases are easier to success and some are easier to HQ)
4) Control vs Item Required Control (The closer you are to this, the less unstables you will get)
5) Craftsmanship vs Item Required Craftsmanship (If you have less than the required amount, you just get lower % on success, this only affects success in the fact it takes more successful turns to advance to 100%, but if you have enough control and other items in your favor, you will success just fine)
6) Magic Craftsmanship (This helps success also, but very minimally, this mostly helps Quality go up on successes, for those that don't believe me, please test this out, my results show this)

I do agree with some of those posts, but the crafting system is not as advanced as you may think, its actually very simple.

No matter how high your Stats Vs Items stats, how perfect moon phase is etc.. you never go above 99% success, there is always a chance to fail. In fact, the game will MAKE you fail if your success % for the last X synths > what you should be at. So expect to fail, you can never be 100% success when synthesizing items above your rank. Below, it can be 99% success.

My Character Profile