On-hit items are not necessarily the issue here
It is how easy attack speed + on-hit items are to get because many on-hit items give +40% for pretty cheap cost wise. They are so cost efficient for better than average effectiveness in combat that many champions are prioritizing them over standard builds. I have been seeing a whole lot more of
"on-hit" 
and 
(pre-revert/nerf that is) than any of their suggested/recommended builds and more often in their off roles than their typical (usually JG).
all have kick-ass on-hit passives and really high attack speed (Youmuu's is the inverse but still counts) which when combo'd with high attack speed can end up dealing tons of damage. This is nothing new of course, it has always been quite a struggle, but especially this season.
My guess is that is all due to this item here:
A little while back this guy never had the passive shots apply crits. Combo this with Rageblade's passive and you really start hurting. But Rageblade is not at fault here. If Runaan's Hurricane did not apply the on-hits of items only (they would still apply ability based ones like Jinx's rockets and Teemo's poison) then I think the game would see less issues around high attack speed on-hit builds and their balancing.
Also on a side note: Does Twitch's ult when used with Runaan's Hurricane and/or Rageblade double, triple, or even quadruple proc on-hits since the ult also applies on-hits?
