Is Kassadin still good in Season 5?

Recently I bought Kassadin because I saw him for a long time, and back in post-season 3 when I joined, everyone was complaining about Kassawin and how he should be banned every game. Eventually after buying most of the champs I wanted, I said "Why not?" and bought him. I read about the nerfs to his kit, but I still wanted to try him out, because he seemed like a unique and fun AP mobility carry. After playing a few games, I was disappointed. His entire kit was extremely underwhelming and lackluster, and damage at most stages of the game was almost non-existent. I understand that I have only played a few games with him, but he seems too weak of a character compared to other melee AP carries. These are the problems I see with his kit.

Passive - Kassadin perpetually ignores unit collision and takes 15% less magic damage. This is one of the things in Kassadin's kit that fits his role. The ignoring of unit collision is a nice thing, but the magic damage reduction is perfect. It solidifies his job as an anti-mage.

Q - Kassadin fires an orb of void energy at a target enemy, dealing magic damage and Silence icon interrupting channeled abilities. The excess energy forms around himself, granting a shield that absorbs magic damage for 1.5 seconds. MAGIC DAMAGE: 70 / 95 / 120 / 145 / 170 (+ 70% AP) SHIELD STRENGTH: 40 / 70 / 100 / 130 / 160 (+ 30% AP)

This move seems problematic. The base damage is not as good as some other mids level one abilities and the shield strength is weak. Viktor's Q is much more spammable and although it gives a weaker shield, it blocks ALL damage, not just magic. It does minor magic damage, but the following auto-attack doing massive damage with the right items compensates for the weakness of the initial strike. Diana's shield has the same AP ratio, but again, it blocks ALL damage. Diana's also can last longer and be stronger. Yasuo, an AD fighter has a natural shield that charges from moving and has no cost whatsoever. Nidalee has a heal that also gives her attack speed, allowing for a faster damage output, and Orianna's shield can do damage, give armor and magic resist, and has a better AP ratio than Kassadin's.

W - Kassadin's basic attacks deal 20 (+ 10% AP) bonus magic damage on-hit. ACTIVE: Kassadin charges his Nether Blade, causing his next basic attack to deal bonus magic damage, gain 50 range (200 total range) and restore a percentage of his missing mana (quintupled against champions). MAGIC DAMAGE: 40 / 65 / 90 / 115 / 140 (+ 60% AP). MANA RESTORED: 4 / 5 / 6 / 7 / 8 % missing mana. MANA RESTORED AGAINST CHAMPIONS: 20 / 25 / 30 / 35 / 40 % missing mana.

The passive part of this definitely helps Kassadin last hit in situations where he is under pressure. Unfortunately, this passive aspect does not go up in damage or ratio as the skill levels up, leaving him weaker if he tries to upgrade it. The 10% AP ration is terrifyingly bad as he needs to get massive AP for the passive to do damage. Teemo's passive gives him easy lasting hitting with an on-hit damage in addition to DoT. Twisted Fate's passive allows him to passively gain strong attack speed, and do the massive 4th hit damage. Teemo's and TF's passives have extreme synergy with the rest of their individual kits, both being able to build attack speed items and still do damage. If a Kassadin tries to build Nashor's, the rest of his moves will do next to no damage. The active is good because it allows Kassadin be able to spam his moves against his opponents for no mana cost. But, energy champs like Akali and Kennen do not mana problems, so they are allowed to spam their moves and then quickly regenerate energy. Resource-less champs like Katarina, Riven, and Yasuo also do not have mana issues, most having spammable moves that let them last hit from a distance.

E - PASSIVE: Kassadin draws energy from spells cast in his vicinity, gaining a charge whenever a spell is cast near him (including his own spells). Upon reaching 6 charges, Kassadin gains the ability to cast Force Pulse. ACTIVE: Kassadin emits a pulse of void energy, dealing magic damage and Slow icon slowing enemies in a 80º cone in front of him for 1 second. MAGIC DAMAGE: 80 / 105 / 130 / 155 / 180 (+ 70% AP). SLOW: 50 / 60 / 70 / 80 / 90%

Kassadin's powerful slow. 90% when maxed. This move has a strong slow and a strong AP ratio with decent base damage. The problem is the fact that it has to be charged with 6 spells, very hard to do unless the opponent has low CD spells. In addition to it lasting only 1 second, it is outclassed by the CC and other mids have. Lissandra has multiple slows, Riven has a small knock-up and a stun, LeBlanc has a slow/root, the list goes on. Compared to the rest of the in-meta mids, 1 second of a massive slow is nothing compared to continuous or devastating slows and other CC from others.

R - ACTIVE: Kassadin teleports to a nearby location, dealing magic damage to enemy units within 150 range upon arrival. MAGIC DAMAGE: 80 / 100 / 120 (+ 2% of max mana). Each subsequent Riftwalk within the next 20 seconds costs double the mana and deals bonus damage, stacking up to 4 times. BONUS DAMAGE PER STACK: 40 / 50 / 60 (+ 1% max mana). MAXIMUM MAGIC DAMAGE: 240 / 300 / 360 (+ 6% max mana).

Once the terror of the game. Now a shell of its former over-poweredness. The range was gutted in the recent updates, the damage all based off of mana, and massive mana costs, although lowered. Because this move is COMPLETELY based off of mana, you have to sacrifice pure AP items for a mix of AP and mana. With a total of 360 and 6% max mana when each 800 mana cast is used, the damage is lackluster. Nidalee has an extremely low CD jump for less mana and can be used more. Akali's ult costs nothing but one charge, does damage based off of AP, and can heal her with spell vamp. Ahri's ult has a longer CD, but uses less mana, and much more damage. Diana's ult can be INSTANTLY refreshed if they enemy is affected with Moonlight, with a high AP ratio and great base damage. Shaco has a blink AND invisibility. Katarina's is nearly instant, costs nothing but a CD that can be refreshed if she gets one kill, and does damage. Lissandra's does more damage and a huge range. LeBlanc can recast her's with her ult and can be used for juking much more easily than Kassadin's. Talon's is like Kassadin's slow but better at all ranks, while amplifying damage. Zed's is available at all levels in addition to having one of the best AD passives in the game. Yasuo's has almost no CD and is an amazing gap closer.

Items: Kassadin's choice of items is limited because of how his skills work. Building full mana will make his other moves do pitiful damage, and building full AP will not leave him enough mana to continually cast his ult. Spell vamp does not work too well, neither does extreme CDR items. The cooldowns are too long, and building a CDR item could have been replaced with a mana or AP item.

Kassadin is in an extremely awkward position right now. If he is buffed, he will go back to "GG DIDNT BAN KASSADIN EZ WIN 4 ENEMY TEAM". If he is left the way he is or nerfed, there his a high chance he may become on the same play level as Poppy and Yorick. There needs to be some balance within his kit. He either needs a complete rework, or some other change that can make him in-meta again. I do want to see change brought to the one who said, "The balance of power must be preserved." Let's try to keep his balance safe.

Suggestions would be very helpful, as maybe we can try to convince Riot to buff him again.