kassadin needs rework, badly.
1. he's mana cost is way too high. he cant even harrass untill he gets some kind of mana regen and mana boost. getting archangel's staff is a must.
2. he only has 2 abilities that can be used frequently. Q and R. his Q's cool down is way too long. his E is not up all the time, and his W is only usable at early levels (1-6).
3. he is a bad laner, and he is terrible at early game.
4. he only shines if there's teamate helping him. he cannot face any1 1v1. he can't even protect tower by himself. due to his long cool down. how could riot games labeled him as an "assassin?"
5. he gets tons of assissts, and people still blame him for Kill stealing. why? back to reason 2. his long cool downs. even with 1000 AP, his comboREWQ, wont do enough damage to kill anyone, not even AD,AP squishies. plus with that much AP he's squishy too, he can not go in next to people's face and melee with W. all he can do is back off, and let his abilities recharge.
I've come up with few ideas to make him more sustainable in lane and better at protecting tower and face people 1v1. make him a better "assassin"
1. make his Q ability cool down shorter by 50 percent. make it 4.5 sec CD instead of 9.
or
2. give the old kayle's passive to him. convert AP to AD, convert AD to AP. if you think convert AD to AP is OP then fine, just give him AP to AD. that way he can get enough melee output making his W more useful mid n late game