Allright, thought I'd follow up with some personnal experience. Last night, I tried the compass theroy. I started making Holy Water at level 43 in Alchemy (it's a level 50 cap item), using light crystals. I positioned myself facing North West (light star), even if it was earth and wind day (did this for a while! )
Well, within 2 hours, I was level 49 Alchemy, passed my Journeyman test with the FireSword and had little failed synth with Holy water. I made about 7 stacks (they sell back to the guild for profit, 150 per flasks) and probably had 8-10 failed synth in total, no HQ results. I also had skill increased almost everytime, even when failing, exept of course at level 48-49.
Results when facing light star:
7 stacks of Holy Water
8-10 failed synthesis
Went from Alchemy 43 to 49 in 2 hours
My conclusion, it definetly helps to face the star of the element associated to the crystal you are using. The compass also states that if youare facing the crescent of that element, you will get more failures but a better chance of HQ results. Have not tried that (was scared of failure and losing money! lol)
I have also disposed of my 10 Flower Pots in different directions, associated with the element of either the seeds, the pot, the crystal given or the expected results... I will let you know in a couple of days!
Hope this helps someone, feel free to share your experience with using the compass!