The way i always figured WoW proffs to work is via percentages.
i.e Orange = 100% chance to level
Yellow = 75% chance to level
green = 50% chance to level.
since when i've made like 100 of something if i stick around to watch, which is quite rare since thats like 1hour, it seems to level to about that degree, give or take some levels based upon luck.
but idk how the game mechanics work,
so if you are getting 100% on yellow, and have tested to the degree of 100s of bandages, then that is an exploit.