Self-experience is a terrible measure for any theory, mostly because your samplesize is so small that is laughable, and does not matter if you think that you gambled a lot and buy a lot of IGG, compare that to the history of all players gambling in D2/D2R and see if your sample size is good enough.
Plus is not like the formulas for anything related to gambling are a secret, all of them are well known.
ilvl = clvl + rnd[10] - 5 to determine the ilvl
Unique: 1/2000
Set: 1/1000
Rare: 1/10
Magical: 1797/2000
chances for rarity
exceptional = 1 + (ilvl - excep qlvl) * 90 / 100
elite = 1 + (ilvl - elite qlvl) * 33 / 100
to determine the quality
Plus a whole inmense guide to explain the item generation process
https://diablo2.diablowiki.net/Item_Generation_Tutorial where you can learn that not all the prefix/suffix have the same frequency, giving you the impression that some have some sort of dominance inside the pool, well because they do.
Anything else is RNG being RNG in a very small sample size making you to belive that there is something else there hidden.