@Riot Sneaky Rat

Let's just think for a moment.

Before the item changes, how often was Twitch seen? Not very often. Heck, after his Expunge nerf, he completely disappeared. He wasn't bad, just wasn't "OP." He has short range without his ult, and his mana costs limit him decently during lane phase. His mid game held a bit of assassination potential, but his late game is where he really shined, due to his ult's piercing effect.

"But Leiton, Twitch was a lane bully!"

Who exactly did Twitch bully in lane? Vayne? Ashe? Kog'Maw? Who else? Lucian could out-trade him. MF was and is far more of a lane bully. Caitlyn destroyed him in lane. Tristana even had more early game dominance due to her substantial Explosive Shot damage. Varus could poke from a distance, which Twitch can't deal with. Corki could escape anything Twitch tried to do, and later could poke him down, and even reveals his stealth.

"But Leiton, Twitch could just Cask->Expunge for massive damage!"

After the Expunge nerfs? Hardly. After the nerfs, Twitch needed to get at least two-three shots off on a target before his Expunge damage would be anything substantial. Which, wasn't a bad thing. Being the late game monster that he was, he needed to have a harder time getting rolling. Which, he did.

"But Leiton, the ADC itemization changes really buffed him!"

Did they? What exactly did they buff? With the BotRK active nerf, his assassination potential went down quite a bit. With the BT nerf, the early game team-fighting potential went out the window. He could always abuse Youmoo's Ghostblade's active for a nicer mid-game fight, but so could everyone else. It buffed ADCs like Tristana, Kog'Maw, and Lucian far more than it ever buffed Twitch.

Now, let me look at the changes...

Base AD dropped by 3, from 52 to 49 (46 + 3/level).

That put him at the lowest base attack damage level of any Marksman, tied with Varus (Who more than makes up for the lack of straight AD with his massive poke and team-fighting changing CC). Twitch already has no wave-clear without the use of his only trading ability, meaning he needed that damage to perform any kind of last-hitting under turret or while trying to deal with the harass of the enemy laner(s).

Passive DoT reduced from 2/4/6/8 per stack to 1/2/3/4/5/6 per stack.

Twitch's passive damage at early levels was already laughable. Passive regeneration on most champions meant that Twitch had to fully commit to a fight, and pull off a full 6 stacks of his passive in order for the damage to go over the healing that a potion offered. Now, the damage is even worse. Late game, it can still deal some damage, but early game, where he was already mediocre, it is non-existent.

Ambush time to stealth increased to a minimum of 1.5 seconds, and a maximum of 6 seconds.

Twitch's main, and rather blatant weakness, is that he has to choose between initiating a fight with his Q, or to use it as an escape. Before the change, it was already an unreliable escape, due to how squishy Twitch is. Three seconds has always been enough time to kill him, and has never been a problem. It's extremely clunky to play Twitch when your Q can now ONLY be used to initiate a fight.

I get that you want to define his weakness as a high risk, high reward champion, but with the nerfs to his damage, the all-but-useless-in-lane Q, the assassinations via BotRK nerf, and the resurgence of people he can't deal with in lane, it's a bit much. A bit TOO much. You want to see Twitch as a late-game monster, but with these changes, Twitch cannot reach the late game, because of how far behind all of these changes put him. I cannot tell you the number of times where I've shot a melee minion, only to laugh at how little damage is done.

I went to LoLKing to see what Twitch's stats were. I don't tend to put a ton of stock into win-rate/ban-rate statistics, but I cannot deny that they do hold at least a bit of merit in most cases. Urgot is banned more often than Twitch. Twitch has, currently, the second lowest win-rate of any Marksman in all tiers. His pick rate has dwindled down to below average for Marksman, and once again, he's completely fallen out of favor.

Twitch was considered viable for two weeks. Two whole weeks, I didn't get yelled at for picking a "useless champ." Only two weeks where he wasn't considered trash to mid tier, and you nerf him into uselessness, without any compensation buffs.

And for an example of just how pathetic Twitch's damage is, here's a video. https://www.youtube.com/watch?v=GdF3BdZpdHA

Notice, Twitch completely outplays the Braum/Caitlyn, who clearly should have an advantage in this matchup. Dodges the Qs, dodges the ult, blocks the Caitlyn ult from Janna, he does absolutely everything right, but because of how weak his damage is, Caitlyn/Braum end up even in the trade.