Originally Posted by Hydrophobic
RFC -> Rapid Fire Cannon
No lethality cap AFAIK.
Correct me if I'm wrong, but don't diminishing returns kick in depending on team comps in particular? Full stacking arpen+reduction gives you either 74 lethality + 30% reduction + 7% reduction = effective 113.67 for Ferocity tree or 82.4 lethality + 30% reduction = effective 117.71 for Cunning, enough to do true damage to anyone with no armor items except Rammus or Garen.
Median armor at 18 is only 78, so even after standard armor seals you only need effective 87 which can easily be reached while skipping one of EoN / Duckblade / marks. And that's even before having a Sion or Vi or Jayce or Corki, or something less meta, on your team.
You're still getting flat -15 armor , of course, but that's only better than the -45% bonus you could spend the slot on against Vow, Locket, Tabi, or Zeke's without armor seals, or only against Vow with.
(writing this makes me realize i've been doing MF wrong. But do I drop EoN and its active that lets me finish an ult channel, or Duskblade and literally the only sweeping my team does?)