He has it all. 1 to 6 dashes/blinks
A HUGE movement speed boost
long aoe stun
a Hook, that can throw people over you
one of the strongest self-heals in game. He can comeback with almost full hp from being out of sight for a few seconds, so if he "fails" his mission he can go an do it again without having to back.
Execute with an indicator.
Personally, I feel like the hook, dash/stun and execute, are too much a part of his identity to remove. So I would look into the other things, preferably starting with his heal. He has 2 passives, and I think that the other passive is enough. It makes him too safe, so while he can already escape any situation, he can nullify everything you did to him, as he heals it all back up again. Most other assassins do not have all of these tools to help with assassinating, Twitch only have has an invisibility that is delayed if he takes damage (unlike the instant invisibility of pyke), khazix has 1 jump that is able to reset, ahri has 3 small dashes tied to her ult which has quite a longer cooldown than any basic ability, and a charm as cc (and she is even considered quite hard to balance as she is always in the meta due to her powerful kit, and she has less tools to utilize than pyke) etc