the idea that the 15% lootfind stacks has been confirmed on other th forums. to prove it, go do a quick helhiem run, from beginning to end and kill hel, make sure to have your 15% loot drop on. then i will go with you on another run, and i garuntee you will get 100% more items then the first time. Someone elsewhere explained it better then i can,... but

basically it doesnt mean you havea 30% chance of finding your elite, it means you have a 30% chance of finding more items, which in turn increases your chance of finding elite items. something of that nature.