User blog comment:Riuzak/Custom Forecast Patch 4.13/@comment-3974211-20140719024301/@comment-3974211-20140719150056

(100% + 100% + 100% + 250%) / 4 = 137.5%, which means Infinity Edge is netting you an increases in damage of 37.5% by itself (let alone if you get some crit chance). Having Bloodthirster increases bonus AD by 10% is just a weaker version of Infinity Edge, which combined with 20% lifesteal will likely be overpowered.