Sett's true damage is fine just dodge the dam true damage zone. or poke him and not fill his grit all at one time.
Yasou's W is also fine for its duration its hit box needs to be slimmer so he cant sit in the W and be protected from both sides. ranged champion just need to learn to play around it. Lowering Yasou's durability and mobility will be good if we need to look at anything else we need to decrease his crit damage more as 10% crit damage is not = to double crit chance and lower the base and ad ratio on his ult or lower the Bonus armor pen amount and duration after his ult which is already a nuke in itself 20% bonus armor pen after a nuke ult for 6 seconds is fine considering his spells are on low as fuk cooldown he doesnt need a whole 15 seconds and to be protected from needing to build last whisperer or black cleaver while also getting the most broken ad item infinity edge as a core item due to how his kit removed.
Trumph just needs the gold removed other than that id say it needs a healing buff to probally 18% rather than a nerf or if it needs a nerf let the nerf be that it takes longer to reach the champion based on distance from killed target.
Illaoi needs her damage lowered not her heal and in exchange allowed more tentecle spawns late game and let the spawn closer together.
Sylas W losing the exicute damage was supid they should have kept the exicute damage and lowered the W's healing while not removing his shield on first E dash maybe just increase the E cooldown by 2 seconds.
Senna no self heal on Q its comming out of a gun why does it self heal. removed movement speed buff after auto attacking. Fixxed auto attacks arent anything special if you then remove the counterplay for their auto attacks being fixed same with jhin.
your Orrn nerfs arent gona do anything until they touch his W then when they touch his w hes going to go back to being the absolute worst champion in the game because they never fixed his one flaw except by breaking his W he cant maintain his strength when he wins his lane
Darius needs his Hemmorage and Noxian might decreased and his E hidden armor pen needs to scale up to 15% max rather than 35% His healing is fine except for that his Q and W needs a longer cooldown because there is no window to go in and take advantage of a long cooldown after he gets 5% cdr.
Nami Ap ratio for damage reduced just that which reduces the damage per bounce. the healing is fine.
Shaco Yes please
Tryndamere Shouldnt be able to ult during CC that was a bad buff if he doesnt want to get instagibbed during cc he and yasou (and ranged carries) should have to build defensive items and not the ones that still give them tons of damage. If tryndamere needs another nerf we could lower his crit from rage to 20% crit since all the crit items got buffed some years ago. or we could make his ult 2 3 4 seconds based on rank like you said but with a reason to level it maybe even give it a cost of 15 range rather than letting it give rage.
Thresh doesnt need nerfs except maybe E cooldown nerf front liners just need to be a viable non instagibable option again.
20% slow on ranged 50% on melee
doesnt need a nerf considering its a shield that starts decaying as soon as it pops into existance so shielding the max amount is actually never possible (unless you get hit by a veigar ult in which case you can sheild the max amount but are dead anyway if the ult is powerful enough to break through your max shield.)