Hey RIOT, Pay Attention and fix this stuff please (actual nerfs/non-nerfs)
Lets start with my 4 year running Kassadin main. Granted I can hardly pull AD Kass back from the all AP rework of 2(?) years ago. And he is currently still an excellent late game champ with a rocky start being a melee champ in a ranged world. That being said, this new patch ruins him. Proof: so lets say he starts with 60 cost R and it's every 3 seconds (because you can splurge early on tons of CD reduction... oh wait). MATH: So that's 60(60), 120(180), 240(420), 480(900), 960(1860). I'm going to stop there because at lvl 6-11 he won't have enough mana to cast any spells and jump away more than 3 times. And unless you build a CRAP TON of mana items (which makes him worthless late game), he will never be able to reach 5 jumps ever.
Kass is an ASSASSIN meaning can get in and get out quick while killing his target. He has a hard enough time doing that now on most of the ADC/APC because of the support or CC lock-downs all other champs have plenty of. And since he has no real lock-downs of his own (E is HARDLY cc), he needs the damage to burst someone down and then get out -- as per the definition of an assassin. Unfortunatly, you stripped him of damage. As flimsy as he is in a confrontation, he has to be able to escape because he has nothing else now. In a big 3v3, 4v4, or 5v5 confrontation, he will get targeted after he jumps in and ALMOST kills someone (you know, 40-70% of their hp if they are a carry). He's already out 1 jump which leaves 3-4 until he's out of mana. He BARELY escapes Tryndamere, Nidalee, Tristana, and good Ahri players as it is (or a good Ashe if he's in a weird place and can't jump over a wall to escape her chasing him with slows). So the answer is to decrease his jump distance, not actually reduce the cost, and call it good? So your logic is... ... ... ... ... Ya... I thought as much. I know he can, like EVERY OTHER FED APC, become a bit overbearing if he gets super fed a lot early on in the game (and 3-4 kills over others isn't actually super fed; he needs 5+). That's really the only argument to this nerf. And it is a HUGE nerf cutting his distance 65%.
So, to sum it up, you have made him unable to do his duties as an assassin. He can't unquestionably kill ADC/APC's (previous patches), and now are removing his ability to be effective at getting in and out of danger/combat. If you have to walk up to the ADC/APC so you can Riftwalk the last 2.5 steps, they have already cc'd him, got help coming, or escaped. Then if you manage to kill them and somehow not die, he dies because he can't jump far enough away to ACTUALLY escape. ***So if you are removing him from being an assassin, where's he going to go besides the junk-pile of worthless champs?
Ok, part of my rant is done. You complain about Kass being too mobile? Lets talk ridiculous mobility:
I see you are fixing Katarina's constant reset of abilities giving her more killing and mobility power than Kass 4 fold (mostly in the damage column). Appreciate that.
Onto Tristana. Granted, her W is key to her kit. However, that she can jump in, kill someone under tower, then jump out, that sounds like an assassin to me. And the range on it is 900? She goes from an untargetable range to killing someone to untargetable range again. She even out-jumps's Kass currently requiring 2 jumps for him to catch up (soon to be 3+ because she has that knock-back remember). So lets compare that to someone who isn't the supposed "master of mobility" (and not Nidalee). Ya, there isn't anyone outside those 2 who can truly chase her by themselves.
Then there is Nidalee. After that partial nerf back 6-12 months ago, where (I'm guessing) enough people cried so you added back some power to her kit, she's now stronger than anyone else in a group fight. With Lichbane and anything more for AP, she can outkite, outrun/escape/initiate and outburst anyone. Her cougar form jumps in and kills anyone from 30% and under in less than 2 seconds (roughly 1-1.5 seconds). Countless games of her pouncing under tower or behind it, instant killing the targets, and then jumping out with 1 or 2 tower hits on her (maybe 10-15% of her health). I have never played with or against a Nid who didn't have ~10+ kills alone by the end of the game. She's a huge threat early, mid, and late game. Her pounce in cougar form can keep her in range to spear or claw anyone she chases, and since pounce costs nothing to her, she can do it 10, 15, 20, 30 times and still have mana. Lets jump back to math for a moment, at 60 mana (her highest cost not true to cost/level) per cast: 10 casts (50 seconds or less if she kills people) is only 600 mana. That's level 8/9 with no mana items; 20 casts is 1200 mana. She can kite through the whole jungle with 20 casts and still have mana leftover to fight with her team who finally caught up with her. Kass has 3-4 (maybe 5) jumps in him before being completely empty of mana. Nid gets a speed increase in bushes and against targets she marks with oh, lets say she spears them for 20-40% of their life depending how much magic resistance they have. Nid is a true assassin who can burst the crap out of anyone then escape all day long.
***So RIOT, how about fixing queen of the jungle and mobility Nidalee who can out-run/kite/chase circles arund Kass BEFORE this patch goes through and is a joke of a mobility contest after the patch? At least with Kass, if he jumped under tower to burst someone down, he had to walk out taking 1-3 tower shots. Nid and Trist can dive without a second thought. Kass used to be able to burst down 80-100% an ADC/APC by himself and escape losing a good chunk of his mana pool. Nid DOES burst down 80-100% (end game she can pull 2000 damage if you don't have enough MR and HP which aren't standard ADC/APC items needed) on EVERY pounce, and can pounce all day long pretty much free of mana cost.