@Meddler Regarding Thornmail Changes
I am writing this in response to your response on 7/18/2017 regarding the "split [internal opinion] between right ballpark and too strong" of bramble vest (and by extension thornmail).
While I agree that tanks and bruisers need an item to prevent them from being a "health battery" for carries, I think this iteration missed the mark.
On items where grievous wounds is healthy, burden of application is the responsibility of the item user.
Executioner's Calling/Mortal Reminder and Morellonomicon both require the user to complete certain requirements to apply the debuff. Thornmail, by contrast, is a passive effect that doesn't require the user of the item to do anything; burden of application is not on the item user.
Thornmail, in its current state, penalizes opponents for good play rather than rewards players for good play.
With this in mind, I would propose turning the application of grievous wounds on thornmail into a thunderlords like proc; damage or CC a champion X number of times within Y seconds to apply grievous wounds for Z seconds. Allowing things like sunfire cape and thornmail to be part of those procs and with sufficient number tuning, the player who bought thornmail is rewarded for good play.