New keystone runes
Ok. Sience we(players) do not have any additional info about keyrunes that you have shown us. Here are my concerns about them and as you will be able to see, each one is reasoneably justified.
Berserker. It will be out of balance for champions that have self buffs.
Toplane :
(the 5 attack 1s combo)
Adc:
Junglers:
Midder: 
Perxie. It will be out of balance for champions that have single HUGE burst dmg.
Judging by the short film that you Dev have shown us Perxie has 3s cd before another use which if I am correct gives you 1 skill boost per 3s and you have to "come and get her" If that is the case then:
Toplane:
E with Perxie, then flat W, flat Q, and R with Perxie and byebye full tank Naut
Perxie + Boosted shot beybye 1/2 hp of anything
Normal barrels if that dude gets farmed are op but with Perxie - Angel of deth has come from the barrel of the Black Pearl
"Here taste my Perxied Q" - annoyment to whole new level - 20 out of 10
Mid:
"Tibbers go F*** them"
"The balls of judgement"
"Owh teamfight? They have 3k hp ? HERE GOES PERXIE BOMB"
"Best assasin always tresure the Perxie"
"PERXIMACIA HAAAA!!!!"
Supports:
"Perxie and Pixie my 2 best friends to change someones life in to a living hell"
And now THE BIGGEST OVERPOWER that you could possibly come with. THE OVERHEAL. I again remind that I am judging only by provided data. IF "Overheal" gives you and your teammates armor of value of 100% of heal you cast and they recive then.
Toplane:
"DethDance+Sterak+SpiritVisage - 1 v 5 ? Sience when is that a problem?"
"Well there were 5 of them at Nashor pit, I just felt I have to solo them before I took Nashor"
"Does anyone need free AOE shield ?"
"U wanted to kill me ? I am Drakulla MOTHA F****"
Supports:

The whole new meanning of PURE AP builds
Those examples are just a tip of the iceberg because of WHOLE new poke avalibilities of perxie, OP shields/immortality of overheal and limitless AS of berserker.
Now reasonable solutions. Berserker - DON'T remove AS cap under ANY circumstances, just DON'T. Even for a brief time. Cuz 3s is all what good Twitch player needs to kill whole enemy team as it is NOW. I do not even want to immagine what will happen if you remove his AS cap. Overheal - 2 solutions:
- Shield can only stack up to 10-20% of max HP of caster/target
- Shield can stack 100% of heal recived but only for duration of 2s then 5-10s cd That should prevent PERMA bann at Illaoi, Darius, Vald, Fiora and Aatrox Perxie - 1 use per 10s never less cuz Annie, Syndra and Zed will get perma bann anyway. That will at least keep Ahri, Vel'Koz, Akali and Xerath players happy.
Those were my concerns and solutions I came up with. Thank you for reading. For all vocabulary mistakes I am humbly apologising but I am not native english speaker. [slayer-pantheon-thumbs]