Most astounding thing about PBE thornmail:
#It actually makes some degree of sense to build it on Ashe!
More specifically, by helping her duel other ADCs.
-GW to negate lifesteal -Cold Steel to slow down their autos -Damage Spike -Both Armor and health so it gives a little more general defense
Seems like the perfect core item Ashe was missing.
Kappa
, being used to counter 
and other nonsense hyper dash champs. I told you guys the FLASHDASHers would abuse it, and they damned well made it core on their builds.