The one major thing that Riot needs to re-balance across the board in pre-season

HEALING.

Over the last few years we have been seeing 1 major mechanic in the game slowly disappear from items and champion kits, Grievous wounds(GW). In the past when healing has been brought up Riot members have always pointed out that healing and sustain have to be balanced around the fact that GW was in the game and somewhat prevalent, they had to balance out healing so it still felt somewhat useful even when being cut in half. Which was fine because there were plenty of different ways to obtain GW and counter the healing, BUT over the last year or so we have lost all GW from items and champions except for 4 sources, Katarina's R, Varus' E, Morellonomicon, and ignite. While that is not a bad thing by itself, the problem is that even after this mechanic has been removed more and more from the game these ridiculous healing numbers haven't been lowered. Riot needs to do a across the board re-balancing of healing to account for this.

I remember reading this thread last year, it was mainly about the (now shelved) Warwick rework where ZenonTheStoic brought up some really good points on GW as a mechanic and healing in general. Xelnath also chimed in some good points in his comment. http://boards.na.leagueoflegends.com/en/c/live-gameplay/obkTq9My-lets-talk-grievous-wounds

TLDR Healing has always been gated by the fact that GW was prevalent, but now that it is all but gone the numbers need to be re-tuned.