Kassadin feels outdated
Other than his passive which removes the tilt from being creepblocked, the rest of his kit is very clunky. He lacks the stealth for engages and on demand escape like other assassin. Look at champs like LB/Zed/Fizz. They can engage, then blink out, or bait out CC to escape. Kass has none of those. Kass goes in blow his rotation, then is stuck in the fight without any escape. Then we have Shaco/Rengar/Eve who can stealth in for a guaranteed 100-0 while an approaching Kassadin is spotted from miles away. Kassadin damage is lackluster as well and despite being a late game scaling champ, most games are decided by 10 minutes before he can even scale. In his current state, he doesn't need buffs, but rather for his kit to be brought to 2018.