Is Kayn too Overpowered?

So today, went into another League of Legends Teamfight Tactics rated match, I missed 6 stacking Ninja comps in the past, so I wanted to give the Shadw/Ninja Comp a try.
While I started off with an Exile champ, it did practically handed it to me during round 2. So why not, easy start off right..
I wasn’t expecting it at the very least but, Yellow Hero Kayn, felt a little too overpowered.
I was struggling to cope while I was collecting my Ninja, using any champs as fillers until I gotten 4.
I was on the verge of getting eliminated when RNG gave me a Kayn.
I didn’t think it would of mattered THAT much but it completely rekted the other time alive.
Kayn Skills
Reaper
Active
Mana 0 / 50

Kayn dashes toward his target then slashes all adjacent enemies, dealing magic damage and increasing the cost of their next spell by 33%. If the slash hits exactly one target, Kayn immediately casts again. As Rhaast: Reaping Slash heals Kayn for 50% of the damage it deals. As Shadow Assassin: Reaping Slash deals an extra 50% damage for the first 10 seconds of combat.
Damage: 375 / 555 / 6666
Origin

Tormented
Tormented can be transformed after participating in 3 combats, enhancing their abilities.
Class

Shade
Innate: When combat starts, Shades teleport to the enemy backline. After every third attack Shades dip into the shadows, stealthing and causing their next basic attack to deal bonus magic damage.
2 – 125 Bonus Magic Damage
3 – 400 Bonus Magic Damage
4 – 750 Bonus Magic Damage
While there are only 3 Shade Champs in the game, you Must get a Fated Shade Champ to activate the 4th Shade skill
Kayn 836 non-crit hit TFT 4-4 Hero Choice 5-1 Kayn pre-match 5-7 Boss fight melt Settt Active Exposion Evelyn Active Skill