Dark Harvest: I honestly think that this rework is very good!

While maybe its numbers need some adjustment, the mechanic itself is much better imho.

It starts out abysmal (huge CD, low damage), then scales very well - like it did before. But now:

• it helps in mobile vs immobile matchups: how many times have you caught that Zed out of position, only for him to slip away with 10 hp because you can't chase him? Well, now you still get an additional something worthwhile out of it!
• it incentivizes fighting: it won't scale if you don't take risks, and those risks are higher than before because of its low damage and high cd early
• it procs on spell casts -> mages can finally take it and use it lategame too!
• it resets on takedown -> it's a good keystone for AoE mages (e.g. Fiddlesticks), who didn't really have a choice on the matter for the whole last season

Also, I'm not convinced that it increases overall damage in the game, since it takes time and souls for it to outscale the other keystones.

All in all, I think that this was a very good change. Kudos to you, RIOT!