I'd think it doesn't matter too, but over 4000 kills/looting with my warrior, lets just say 4000.
So 3999 times, my warrior only sees and loots Throwing Boulder. Only once was there anything other than just a Throwing Boulder on the corpse.
Compared to 600 kills/looting on my wizard and he has looted 600 Throwing Boulder, 6x Stone of Tranquility, 4 Scale Ore and one ornament.
I know in expansions like TDS if you do a loot X item quest per group member, if all 6 has none of the items needed, every kill usually drops a high number of that item. Once you start looting it, the drop rate goes down significantly, so I always killed a bunch of the mob before looting any and the drop rate stayed high for each kill.
I just don't think RNG explains why in 4000+ kills, my warrior only sees the throwing boulder in nearly every single looting and nothing else and then my wizard with only 600 lootings, sees 11 other things on the corpse besides the throwing boulder. I dunno, but I think I'll keep setting my wizard as the looter lol