Pyke has WAY TOO MUCH UTILITY to also be a viable assassin.
His Passive is so unoriginal it's a joke, it's literally just INSANE SUSTIAN on an assassin who doesn't need it. It's just a buffed Tahm Kench E passive.
His Q is: A short range nuke with an insane slow, OR a long range pull/flip ALSO with an insane slow.
His W is Stealth, it enables his passive while in combat, AND is an escape, gives movement speed.
His E is a dash with a stun that also does massive damage.
His R is a: AOE ranged execute that scales with AD, deals true damage, does damage to everyone around it, it resets, it shares gold, it dashes him, and you don't even need to land it for it to reset, if someone dies under it you still get the gold and reset.
The 1 shot combo on Pyke assassin is W -> E -> Tap Q -> R
The teamfight Pyke is E R R R R R R R R till everything is dead.
The support pyke is Q E Ignite R R -> double kill
He just does TOO MUCH SHIT
CC in his kit: Q slow, Q pull, Q flip, E stun, Death on R
Mobility in his Kit: W movement speed buff, E dash, R dash
So to recap, he has 1) Sustain to fight even if he lost, 2) 3 different CC types, 3) 3 mobility spells, 4) AN EXECUTE THAT SCALES WITH AD THAT DEALS TRUE DAMAGE, and apparently the highest base Armor stat in the game at lv18