[NEW] Champion Concept #2 [Walter, The Experiment]

Alright guys, my second champion concept is a little out of my comfort zone because it's a bursty AP mage. As a top main, this champions ap scalings and base damage might be and probably are unbalanced. I tried using numbers from already existing champs to make it seem more balanced but I want the community opinion. Also, just a reminder, the pictures I use are only the pictures that inspire me to create the design, i don't own the photo. I found it on google. Anyways, here's Walter.

Champion concept: Walter, The Experiment
Ranged AP Burst Mage
@ lvl 18 - HP: 1884.4 , Mana: 1246.4

Backstory: Walter was a human that was experimented on by a mentally disturbed ex-surgeon in Zaun but it went horribly wrong. A machine became overloaded with electricity and exploded, causing an immense blast of heat and lightning, fusing half of Walters body to an endoskeleton nearby and Walter fell unconcious. When Walter awoke, he was surprised to be alive but now he had to live with this hideous deformity. Distraught with his new form, Walter joined the League of Legends. He figured he’d either die or become world famous, both outcomes seemed alright to him.

Passive: Charged Blood
When Walter hits an enemy with an ability, they gain a stack of Blood Charge and for the next 4 seconds, ally auto attacks (including walter's) add additional stacks. At 4 stacks, the enemy is slowed by 70% that decays over 2 seconds. Each target can only be slowed once every 10 seconds.

Q: Lightning Blast (CD - 13/12/11/10/9 seconds) (Mana cost - 40/55/70/85/100)
Walter fires a bolt of lightning in a target direction, dealing (60/80/100/120/140 + 50% AP) damage to all enemies hit and applying a stack of Charged Blood. If the fourth stack of Charged Blood is applied by this ability, the enemy unit is stunned.

W: Storm Volley (CD - 18/17/16/15/14 seconds) (Mana cost - 50/60/70/80/90)
Walter jumps backwards and then fires 3 spheres of energy each with a 0.5 second delay between them. Each sphere deals (60/75/90/105/120 + 75% AP) magic damage and applies a stack of Charged Blood.

E: Electrical Pursuit (CD - 20/18/16/14/12 seconds) (Mana cost - 40/50/60/70/80)
Walter dashes forward (Corki's dash range) and leaves behind a trail of electrified ground for 3 seconds. Any enemy unit that steps on the electrified ground takes (25/50/75/100/125 +40% AP) damage and gains a stack of Charged Blood. An enemy can only receive damage from this ability once per cast.

R: Overloaded Circuits (CD - 120/105/90 seconds) (Mana cost - 100/125/150)
Walter jumps forth and turns off his limiter causing pure energy to explode in every direction dealing (100/140/180/220/260 + 55% AP) damage to all enemies within range and applying a stack of Charged Blood. After 1.25 seconds, a mini implosion happens on Walters location pulling all enemies in range towards him and dealing another (50/70/90/110/130 + 30% AP) damage and silencing enemies hit both times for 0.75 seconds.

It would be great to get feedback on how Walter could be further balanced, and whether you'd like to see Walter as a champion in League of Legends or not.