OP, I respectfully but wholeheartedly disagree with your post.
Riot is basically acknowledging that they will favor champions with LC$BIGPLAYS potential.
And this is a problem? Is the fact people enjoy using or watching certain champions who make flashy plays in and of itself problematic? No. It's not. It's not about the "LC$BIGPLAYS" that make Zed annoying, it's strictly his overbearing strength with the current iteration of in-game balance.
All in all, Zed is one of the best examples of what we call a "healthy assassin" in League of Legends.
Judging by the quotation marks, I, too, can see that Riot was "totally serious" when they said he was "'healthy.'" This is sarcasm, clearly. But let's look at what it's combined with, as you said, because that's more important. You complained about this:
That doesn't mean there aren't problems - while Zed's ability to delete squishies with a button press and some smooth moves is going to remain intact...
And Veigar can't?
And Katarina can't?
And Annie can't?
And Talon can't?
And Master Yi can't?
And LeBlanc can't?
And [insert other assassins or carries here] can't?
The point makes no sense. Riot said nothing about keeping his escape totally intact. Riot made no claims that he wouldn't get hit with nerfs that made him more balanced and fun and strategic to play as and against. Riot simply said that Zed, classed as an assassin, will still maintain his ability to assassinate squishies, as that is the primary job of an assassin. Furthermore, with possibly the exceptions of Master Yi and Katarina (and Akali, possibly), this means that once their load is blown on said squishy, they are left with an even less than optimal kill and teamfight potential. As much as those Zed shurikens hurt, after he's used his Death Mark, he ONLY has those shurikens. And as a squishy melee, he's super vulnerable to simply jumping into a teamfight without that ultimate, regardless of how powerful he is. This is a distinct disadvantage of most (not all) assassins, and it's a very clear weakness. What does Talon do once he loses his ult? Spams W until someone steps out and he can E in again. What does Akali do without her ult? Sits around and watches the teamfight from afar with minimal impact until she gets a new charge.
So yes, he will maintain his ability to delete super squishy targets, like an ADC, if they get in range and are out of position, as is his role as an assassin. Just like all other assassins.
As another member stated, Riot has clearly pointed out that his kit is very problematic in the current iteration of game balance. It's not fair of you to nit-pick the way they chose to word it, especially when they're doing their best to make these patch notes interesting to read rather than the pages and pages of bland documentation that they truly are underneath it all.