Kassadin: A brief history, and a study on "balance" changes (Response PBE's 450-range ult).
My first champion I wanted to play in League was Kassadin 
. I knew nothing about the game or the champion, but Riftwalk looked extremely cool, and I knew I would enjoy a champion with the ability to reposition himself that frequently. A friend showed me the xPeke backdoor, and I was smitten. was life.
Of course, it didn't take very long in League to realize I had basically sided with Satan himself. Not a Christian ideal of Satan (whom some would side with), but rather the concept of pure and unfathomable evil. I played Kass constantly in norms, and then when I hit level 30 discovered that he was running at a near 100% ban rate in ranked. Since he was basically the only midlaner I played, that wasn't ideal for me. I had to learn to "main" other midlaners who I would actually have a shot at playing.
Kassadin nerfs came and went... the one where half the mana cost was refunded if you riftwalked onto enemy champions was so funny I still can't understand how someone thought that was a good idea (that was the point at which I stopped going 
+ 
, since the mana sustain was no longer a problem with just 
). And then the rework hit. I played Kass constantly. I was never not playing him. I wanted to have all the mechanics of the new kit worked out. I spent hours designing item builds for various situations. I calculated runes and masteries that would work well with how I wanted to play him... it was so much fun.
And then he was buffed. I was terrified. Not because I didn't enjoy the buff, but because it was only going to highlight his strengths and I knew a hard nerf was coming in the wake of it. What the "new" Kass had needed was a slightly stronger AP scaling on his W. What he got was that + obscene scaling on his Q shield. As expected, both were rolled back. With the less-than-stellar overall AP scaling in his kit (since the removal of any AP scaling on his formerly 80% scaling ult), other summoners started experimenting with knew concepts for Kassadin... and IcebornKass was formed. At that point, I knew we were headed into dark days. The problem wasn't that Kass was too strong, but rather that he wasn't strong enough. Iceborn was a crutch because mana costs and damage were poorly tuned. If his kit could make use of AP well enough, the miserable AP on Iceborn would have been inefficient, and other builds would've risen.
Instead, the CD on W was greatly increased. Of all the available kit-tuning options, this was what I least expected, because it solved the fewest problems while heavily tilting Kassadin's kit towards disfunctionality. When I had spent weeks pouring over the initial reworked kit, it was immediately apparent that his kit begged for Lichbane to be included. So obvious, in fact, that Lichbane was nerfed in the same patch as Kass' rework was released
[ http://na.leagueoflegends.com/en/news/game-updates/patch/patch-44-notes ] . Because of the refocused kit (with a massive mana-restore built into W), RoA+Archangels was no longer necessary... but there was a trick. Complaints about Kassadin pre-rework (a.k.a., since he had come out) had always revolved around his having "a free flash every 5 seconds"... which presumed some amount of CDR (such as the 20% 
used to give). With the reworked kit, Kassadin's "free flash" was no longer on a 5 second cooldown -- it was 3 seconds. With no CDR. This was the trick. Building CDR was no longer efficient. If you wanted more damage, you built more damage. Kass revolved around the delicate balance between static cooldowns and appropriate use of his W to keep him Riftwalking during fights (when he was burning through mana faster than 
mains would ever imagine possible). You could build CDR to help with your Q/W/E cooldowns, but the kit made it more efficient to just buy damage (My standard build during this time was , 
, 
, 
, 
, 
). With the increased cooldown on W, Kassadin was desperately mana-hungry, and terrifyingly close to needing to purchase CDR just to have his W up more frequently. Lichbane became a luxury item I couldn't bother purchasing early-game.
Reflect on this for a moment: Kassadin players spend the vast majority of every match with Riftwalk off cooldown, and still not being used. And even so, I suspect they still spend more mana in a match than all 9 other champions combined. Because Riftwalk's cooldown isn't balanced. And the only change happening there has been to make it shorter. The point I've arrived at with Kassadin is that unless you are overwhelmingly snowballing, you cannot assassinate anyone. The complaint in previous iterations of Kassadin has always been that his ult's CD was stupid short. The response was to shorten it and give him an offensive way to keep Riftwalking. Except he didn't have enough damage to 1-shot carries, so viable slow-them-down-and-beat-their-face-in builds were developed. So the entire kit was thrown off-balance, and now if you pick Kassadin, you are literally telling the opposing mid-laner that you think they suck and you can play a completely crippled champion and make them look like trash.
Kassadin Live: Extremely low base-damage on spells, no AP scaling on ult, the highest mana-cost in the game, and a myriad of "pick-on-Kassadin" specific nerfs (W-cooldown, no scaling MR, humorous slow-duration on E (although... 
knows all about comical slow-durations), -10 base-damage on Q...). And he's melee. With no solid gap-closer pre-6.
End of "rant"
Proposed changes:
Kassadin's ult needs a real cooldown, and the static cooldown needs to go. Building CDR necessarily removes some available AP-centric buildpaths, and honestly... the current iteration of 
would actually be really cool on Kassadin.
Also, Null Sphere needs to not be point-and-damage. Whether it's an AoE similar to Xerath's W, or a basic skillshot... something other than "Hey, let's trade. You aim something at me, and I hit you with this 100% of the time while getting a shield. Good luck." would probably go a long way to relieving the oppression that has always been part of Kassadin's kit (whenever he has been in a playable state).
Changing his ult range is just... not the way to go about balancing him. People will have to find ways to stick to targets even better, and builds will get worse and worse. Presently, Kassadin builds at least are fairly reasonable for an AP (RoA + Zhonyas + Sorcs)... nothing bizarre. Nerf the ult-range, and I wouldn't be surprised if 
started showing up (or if 
came back). He'll have to be tankier, he'll have to be able to stick to targets... and there isn't enough damage in the game to let him actually kill carries efficiently until late-game.
In a way, I am most saddened by the community's vitriolic responses to Kassadin nerfs -- "he deserves it" is almost always echoed by people who don't even know anything about the poor guy. "Better nerf Irelia" has nothing on the list of "balance changes" Kassadin mains have gone through to date. Yes, I am passionate about this. I don't want him to be "OP." I want him to fulfill my "End-Game Fantasy." I want to play Kassadin and enjoy it. My skills against my opponents. My knowledge of the game vs. my enemies. I am willing to make sacrifices for my mobility -- it's an obviously necessary trade-off. But reducing my mobility is to reduce the point of the trade-off. If I am to be boring and "normal," give me a 90% scaling ult and high base-damage. And no 1000+ mana skills. But please don't actually do that. I want Kassadin to feel like the unique character he is. And for everyone to be okay with that.
Provided for reference -- links to other Kassadin "essays" I've written on the forums
http://boards.na.leagueoflegends.com/en/c/gameplay-balance/GTEyBmHY-can-we-balance-kassadin
http://forums.na.leagueoflegends.com/board/showthread.php?t=4690552
http://forums.na.leagueoflegends.com/board/showthread.php?t=3855459
