Rengar versus Talon

Because Rengar stealth lasts significantly longer.

Also because they're different champions.

Rengars ult lasts way longer. With that logic youd be asking for ! for khazix as well, or anyone with stealth. If anyone deserves the ! it would be khazix not talon, but I agree, they should add some other way of warning for stealth champions.

rengar's jump comes from his passive and his ult, it's free. Talon has to blow a skill to jump to target Rengar can delete people MID JUMP talon immediately blinks to target and probably has to blow his entire kit on the kill rengar can probably go a lot further for a longer period of time that even increases if he gets enough trophies, giving him a lot more room on when to pop his ult costs no mana talon's ult lasts a few seconds at best, also costs mana rengar can proc his Q twice in a row, one of them being an even stronger empowered strike with full fericity talon can use his Q once, no empowered. costs mana

so yeah considering that reng can erase you in the blink of an eye with just one ability, his Q, as long as he can jump from a bush, yea i'd say the exclamation mark is needed there, especially being gated only really by cdr whereas talon needs mana and his whole kit to do so.

Because Talons Ult tells you where he is and where he is going, costs him like 50% of his total damage on his full rotation and lasts only 2 seconds?