User blog comment:MOTZI/Think About It - Hybrids/@comment-24420226-20140331025129

The biggest challenge to a true damage-focused hybrid champion is penetration: while you might have an advantage early in lane because only GA gives both armor and magic res and is rarely picked up as a first item, once people get the chance to itemize for both types of damage, you kind of hit a wall. There is no one item that will allow you to effectively get around both types of resistances, and trying to stack both armor and magic penetration across mutliple item slots is terribly inefficient and won't leave much room for some of your more ideal core items (Gunbalde, etc).