User blog comment:Doc Tam/Flaming Fists, an AS for semi-carries/@comment-80.222.102.9-20120808064847/@comment-4434378-20120808131722

The additional magic damage doesn't crit. When you go AD Kog, most of the time half your damage is Magical. On-hit doesn't work that well due to lack of sustain, but you could optimize your BAB by going Bloodthirster and this item, giving you superior AS to IE/PD, while giving out a higher amount of AD (at the cost of not having crits). This way, you could potentially tack on a Madred's blood razor, and not feel like the on-hit is wasted due to it not synergizing with your critical.

The Fiora strategy page talks about a crit-less build, but it looks dumb because then your only options for non-crit, non-magic AS items are Zeke's and Black Cleaver.