User blog comment:Care Level/Itemization Holes/@comment-12314620-20130826183240/@comment-9593635-20130828011354

I don't think ADCs would use armor pen boots unless the pen increased their damage more than 20% attack speed, which it shouldn't -- the penetration amount should be adjusted to fit that. Also, I'm fairly certain that %penetration stacks multiplicatively, so it's less cost-efficient to build multiple %pen items.

Traditional ADCs playing as AD casters because of Rapier wouldn't be a problem, I think: if Ashe is Volleying hardcore but AAing less-hardcore, she shouldn't be doing more sustained damage. If she is, Rapier is giving too much AD or not penalizing AS hard enough.

The bigger concern, I think, is selective hybridization of the roles by virtue of the toggle feature: what if Miss Fortune toggles the AD boost off, autoattacks through a teamfight as usual, but then pops the toggle before ulting? Or, with our Ashe, what if she AAs as usual, but toggles just before landing the Volley that otherwise wouldn't have gotten a kill? Or Caitlyn just... being Caitlyn.

If bruisers are mis-building and it's shutting them down in teamfights, adding Rapier won't change it: if they would've gone for more damage, anyway, they'll get it from elsewhare.

Seeing the timers on wards is a benefit of Diamond SS that I hadn't considered: that should be accounted for, good call. I talked about clearing them, below, and why I don't think it would be overly powerful in that capacity (unless you're Leona).

Thanks for the feedback.