i'm trying this rune a lot on pbe,and it isn't so OP as it looks:
Dark Harvest One Shot montage
mostly were diamond/master playing vs bronzes/silvers/gold,they get 20+ kills and 15+ assist so they stack it much more as it is supposed to work (it's like complaining about getting OS by a stacked and fed nasus or veigar),that's actually hard to do if you are playing in your elo (don't forget that on PBE a bronze can be matched with a diamond,everyone is unranked so the matchmaking is unbalanced af)
you guys would do good to shave off that type of insta-burst power from the keystone before it becomes another Thunderlord's case
electrocute is basically the same but it can be used from the distance (a fast burst combo would instaproc it anyway),but without the risk of autoattacking someone
sure it needs to be changed a bit,but about numbers:
electrocute 220 + 30%AP + 50%AD,if you have 650 AP 100AD -> 465 damage
edit,i didn't notice this nerf: dark harvest 140 100 + 10%AP + 15% AD,650AP 100AD -> 220 180 damage,so you need 245 285 stacks for getting even (about 30 35 takedown or 49 57 cannon minions or 122 142 large monsters)
the only change that i'd make is to giving it a 30%AP - 50% AD scaling but changing its damange to 60 at all ranks,so it would be the same on full damage champions but it would be a nerf if you are building tank (because this rune may allow some tanky/assassin build such the old fizz or ekko tank)
compared with electrocute,it's a risky but more rewarding rune,if you snowball a lane you get a bit more damage,if you are even you get a bit less damage and if you are losing it's totally useless
so not every champinon can use it,syndra would never pick this one,you need an autoattack in your combo,and it wouldn't work with kassadin or viktor either,because they wouldn't stack this rune so electrocute would be just better,because it will surely scale with your levels and AP
this rune works only with early/mid game champion,allowing them do be something in late if they did their job,instead of seeing your enemy just farming up some minutes and outscaling you like nothing is happened
finnally we got a mechanics that rewards for snowballing,phanteon for example may win his lane,but as hard he can snowball he will become useless after min 15 anyway,actually with this rune if he win his lane he will get a bonus,if he lose his lane or it is even he will end up to become useless
about its resets on kills,sure it is nice but compared with electrocute this rune makes you so predictable,you won't rush untill you get the cannon minion wawe,you will try to trade after you get a stack from minions or monsters (you know he's going to trade you,so you can bait him,or you jungler can gank for example),before 100 stacks its buff last only 20 sec (when you can proc electrocute whenever you want),and if you are getting killed or somehow you are not getting stacks it won't refresh (for example if you are low and you need to back when your cannon minion wawe is coming,you lost it),so trading with this rune is hard even if your enemy doesn't play around it and it also make your all in so obvious
i think that actually electrocute and press the attack are stronger than this,dark harvest is just fun when you are overfeed
edit 2:
with no way to counter-play it after 100 stacks since it lasts so long after that point.
other keystone last for the whole game,electrocute or arcane comet won't go in CD unless you don't use them,so where is the problem if this buff can last 300s if it's as strong as the others? the CD is just a nerf for the early game
+ boots
