Kassadin rebalance

I thought it would be cool if Kassadin had two playstyle options:

1. Burst Assassin (primarily AP based)

2. DPS Fighter (primarily Mana based)

Here's what I came up with. :P

Void Stone (Passive)

Kassadin takes 15% reduced magic damage and ignores unit collision.

Null Sphere (Q)

RANGE: 650 COST: 80 / 85 / 90 / 95 / 100 MANA COOLDOWN: 10

ACTIVE: Kassadin fires an orb of void energy at a target enemy, dealing 70 / 95 / 120 / 145 / 170 (+ 70% AP) magic damage and forming a shield around himself that absorbs up to 40 / 70 / 100 / 130 / 160 (+ 3.5% of max mana) damage over the next 1.5 seconds.

Spells cast near Kassadin (including his other spells) reduce the cooldown of Null Sphere by 1 second.

Nether Blade (W)

COST: 80 MANA COOLDOWN: 8 / 7 / 6 / 5 / 4

PASSIVE: Kassadin's basic attacks deal 20 (+ 10% AP) (+ 2% of max mana) bonus magic damage on-hit.

ACTIVE: Kassadin charges his blade, causing his next basic attack to deal 40 / 65 / 90 / 115 / 140 (+ 6% of max mana) bonus magic damage and interrupt his target.

Force Pulse (E)

RANGE: 350 COOLDOWN: 16 / 15 / 14 / 13 / 12

ACTIVE: Kassadin drains the area of magical energy, dealing 60 / 85 / 110 /135 /160 (+ 80% AP) magic damage and silencing nearby enemies for 1 second.

For each enemy hit, Kassadin restores 3 / 3.5 / 4 / 4.5 / 5 % of his missing mana ( 7 / 9 / 11 / 13 / 15 % of his missing mana against enemy champions).

Riftwalk (R)

RANGE: 500 COST: 100 COOLDOWN: 5

ACTIVE: Kassadin teleports to target location, dealing 80 / 100 / 120 (+ 60% AP) magic damage to nearby enemies on arrival. He also gains one stack of Phase Shift for 10 seconds, increasing his attack speed by 10%, stacking up to 4 times.

Each stack of Phase Shift also doubles the cost of Riftwalk and adds an additional 40 / 50 / 60 (+ 10% AP) bonus magic damage.

MAXIMUM MAGIC DAMAGE: 240 / 300 / 360 (+ 70% AP)