I already see your main flaw and I'm not even done reading.
You're comparing glass-cannon assassins to sustaining duelists.
Finished reading.
Zed and Talon share completely different functions and playstyles than Trynd.
Assassins are MEANT to get in, kill their target, and get out. Talon, Kat, and Kayn's mobility are fairly conditional. Rengar has no major mobility aside from his jump.
Zed has his shadows, Leblanc has her thingies, Fizz has his pole, Kass has his... R... etc.
They get in, kill whomstever is a problematic champion, and get out IF POSSIBLE. They have a specific rotation they need to use in order to secure the kill, and if ANYTHING fucks it up, they're dead. They don't have much in the way of sustain when things get hairy. Just a way out. They've been designed for this purpose.
Duelists like Tryndamere and bruisers like Kled are meant to deal damage while sustaining until either them or their target wears out/dies. These two build lifesteal for a reason. They aren't AD Casters like Talon, Zed, and even Ezreal. Their kits are geared towards right-clicking to win. They aren't supposed to get out. They aren't meant to target one specific person. Just keep the heat off their team as long as possible, and secure towers via splitpushing (Zero Damage Trynd, anyone?), or helping engage via Kled's R. If things get hairy, they have tools to their advantage. Kled's Skaarl passive building up Courage, Trynd's R/Q, Fiora's R/W, etc.
Giving Zed a one-minute timer for using his shadow to escape is literally destroying his role in the game as a whole (hey that rhymed). You no longer make him an assassin, nor a diver, nor a bruiser, nor a duelist. You've made him... nothing. Literally just a champion who has half of an assassin's kit, with no other notable characteristics. Diana has the engage of an assassin, but she deals damage and tanks damage, hence her classification as a diver. Zed has the engage and disengage of an assassin. So does Kha6, as well as Leblanc.
You'd have to remove Kha6's E reset, and give literally any hyper-mobile assassin a change.
Change Kha, change Leblanc, change Akali, change Zed, change Talon, change Ekko, change Fizz, change Kass, and change Kat. All of these champions were designed with the core concept of getting in, killing your target, and getting out. The whole point of an assassin is to assassinate, and escape.
Imagine if all assassins throughout history went for their kills, then stood there after killing their target. Whoop-dee-doo so reliable. They're supposed to escape so that they can't give the target's allies any intel. In League's case, so that they don't give the target's allies any kills/gold.
To relate my argument to a famous assassination, Gavrilo Princip. One of six assassins assigned to a mission. His was to assassinate Archduke Franz Ferdinand of Austria and cripple the nation's provinces so that those very provinces may be combined into Yugoslavia. Princip's mission was to kill Ferdinand and his wife, then escape. In the event that Princips either failed the assassination or was (about to be) captured, he was given a cyanide pill. However, this pill was out of date, thus he was cucked, being captured and thus imprisoned. The idea of assassins in this game is to not get captured, or for a better term, killed. Do your job, get out. Just as Princips was meant to do, but there is no cyanide pill (executing to tower does not count).
Now, to relate my argument to an ancient Roman story, the story of Horatius Cocles at the bridge. Horatius Cocles was a Roman officer in the late 6th century BC. He was responsible for defending a bridge. Not any bridge like the one on Howling Abyss, but a very, VERY important one. The Pons Sublicius, which connected Rome's walls to the land beyond the Tiber River. The army of Clusium, another ancient city, marched on Rome. The Romans fought all they could, but eventually, they knew they had to bring down the bridge so that the army of Clusium could not invade. Horatius with two others helped fight against the forces. Eventually, Horatius had the other two leave, and while they were escaping and the bridge was being taken down, Horatius fought off every single Clusium invader he could until his allies were secured. He then dove into the Tiber River and miraculously made it out. He didn't have a specific target. Just keep the heat on himself while his team does shit. Same idea with Trynd. Fight until the bitter end for your team, and if you manage to get out at the end, good for you.
Your argument was completely invalidated the moment you used Tryndamere alongside Zed and Talon. As in my historical examples, they shared different goals and different methods. Horatius fought whomstever, and Princips had a specific target. Princips was meant to get out, but Horatius didn't think he himself would have lived. Two different playstyles with two different expectations for an ending once their goal was achieved. Same exact thing with Zed and Trynd.
