IMO, greninja has too many huges flaws that, considering they're not compensated anymore by op moves (old usmash, up b etc...) that make him unable to rise to the higher tiers and will leave him in mid tier in his current state:
:..
-his standing grab is horrible, making him unable to tomahawk properly in high level matches and ruins his shieldgrab options.
Consider this: the tomahawk's basis is to 50 50, will I jump, and do an aerial? ==> answer is to shield then grab.
or will I jump, fall, take advantage of that shield and then grab, bypassing the armor and winning vs shieldgrab.
With a 16-17frame standing grab, that won't happen. I can obviously try a jab after landing, but then again, that'll be beaten by the shield. It makes shielding vs greninja a way stronger option that vs many other characters.
For the shieldgrab well... You already know it I believe. Yes, you'll be able to shield grab laggy moves, but then, you'd be able to do it with anyone. Now try it vs character with a fast recovery aerial, even vs a greninja nair decently spaced. And also, it means that if someone tomahawks, you have to jab, no grab option there (or you're ballzy and predicted that no aerial is incoming, therefore prepared your grab in advance).
-he has startup on his aerials that could trade damages
Situation: you're getting thrown in the airs, then oponnent jumps to you with an aerial. Many characters (think 90% of the cast) have an aerial that can trade for a 50 50, meaning they can airdodge, jump, or hit. greninja has one of these options removed, which makes him more predictible.
-His up b's ledge rebound bug. Ok it doesn't happen too often, but over the course of a tournament it may happen once or twice. That's two stocks you gave for free. That's two games you might have given up for no reason whatsoever.
-the shuriken in his current state is far from being a top tier projectile. Yes it was on 3ds, but atm, you have to use it extremely scarcely to make it a decent move; considering you have no down b and your side b is a hard read, you lack options yet again compared to higher tier characters.
Outside of that, greninja still has tools, but his neutral game is far from op, his combo game is decent without being the greatest and he relies a lot on reads to be used properly. Overall the issue with this character compared to other top tiers is that he requires more "bets" that other higher rated characters to do the same job. Yes he has great tools but his flaws really set him back in the current state.
On a side note, I think his flaws are greatly reduced in 2v2 which make him possible high tier then (having good mobility, great killmoves and decent damages while having a good projectile that can cover some camps).
I'm still loving the character, he has some awesome tools (side b to counter sheik's and diddy's fsmash always was one of my favorites) but seriously I hoped really hard that one of those issues would be corrected in the patch. (hint: usual grab frame for a fast character that is non tether is 6-7...)
tl;dr: pls sakurai stop be mean :/
I won't argue that his standing grab isn't terrible in situations close to the opponent, but I will say it comes out frame 14, which is a ton better than frame 16-17. However, Greninja should never try and play on top of the opponent if approaching from the air. I feel that Greninja is a very zoning oriented character. He's fast and has excellent mobility, yes, but I personally feel that mobility needs to be used for zoning rather than rush down tactics. That said, Greninja still does have a form of Tomahawking. Rather than grab, though it's jabbing the opponents if they try to grab. Greninja's jab excellent, and mixing up Nairs (and even whiffed Nairs to jabs), Fairs, and empty short hops to jabs is an effective strategy. However, his standing grab does serve the important purpose of being a gigantic grab that can outspace some other moves (and grab non-disjoints). In addition to all this, his running grab, while still only coming out on frame 9, is one of the longest in the game and excellent given its range. I'll fully admit, Greninja's shield game is appalling, but I feel his mobility somewhat circumvents this at least.
Yes, Greninja doesn't really have any quick, long lasting aerials like a lot of characters, but he still has excellent airspeed and one of the best movement options in the game in Hydro Pump. In a lot of cases where character can throw out an Nair, all Greninja has to do is jump away and try to land (difficult, but fall speed helps a lot). Against faster character, this is admittedly a problem, but I'm not vouching that he's in any way a top tier character.
Up-B ledge rebound isn't a bug. It's a recovery weakness. You can argue that plenty of top and high tiers had these very minor weaknesses. It can happen by accident, but it's not random. Sheik can also kill herself by side-Bing accidentally as can several other characters. Diddy himself had some weird up-B glitches. Greninja has one of the best recoveries in the game, and I don't think a small flaw that can be mostly avoided really change that too much.
Shuriken is super MU dependent. Some characters do have trouble getting around it; others do not. Either way, it's a good long-range pressure tool. I wouldn't use it at all against a character like Fox, but characters like R.O.B. and Shulk definitely have issues with it.
Outside of all of that, I'll bring up some of the reasons I believe he's a high tier (definitely a low one, though). First of all is his keepaway game. I honestly believe that a Greninja with a stock lead becomes a top 10 character. Greninja has so many options to play a fantastic zoning game. Fair and Bair are both safe on most shields (curse you Sheik). Hydro Pump gives us incredible air mobility. Our mobility in general makes it extremely difficult to catch us. I played an excellent Mii Brawler (2nd at a 132 person tourney) pre-patch recently and noticed that, as long as I got the stock lead, it was difficult for him to even grab me because of how tight Greninja's defensive game can be once he gets that lead. Additionally, Greninja has a kill throw. Combine this with his excellent dash grab, and we have a reliable way to kill people with one
big stipulation. Greninja cannot die before the opponent.
Greninja's biggest weakness, in my opinion, is that he
needs to have the lead. A Greninja with a stock deficit falls to the level of a bottom Mid tier. His kill throw is essentially entirely contingent on rage, and at 0%, it is extremely weak. Worse yet, the opponent has the rage to actually combo Greninja despite Greninja's low percent. Dying before the opponent, in a lot of cases, gives them a free 40% on you.
Finally, if predictions are true, Greninja is going to be in a metagame where three of the best characters in the game are going to be Rosalina, ZSS, and Yoshi, all three of which he has little to no issue with (except ZSS. Haven't played a single ZSS ever, so I don't have an opinion on the MU). Yes, he'll have difficult MUs with Sheik, Fox, and Sonic, but those three may not be as prominent. Now, if I'm completely wrong on this front, then I could see Greninja staying in mid tier, but I do feel this patch has removed some of the roadblocks Greninja had to being a high tier character.
But... high tier, mid tier, whatever tier, I'm going to keep playing the frog regardless of where he ends up. I do personally believe that the character has more potential to succeed now.
Basically, my argument is that Greninja is a solid character that, in my opinion, does better against the top tiers than the other mid tiers. His mobility alone gives him a surprising amount of options, and while he does have abusable flaws, I think he has an overall better kit than any other mid tier at the moment. I will admit, though, he'd probably be the hardest high tier to play as since there isn't any one thing you can really rely on with him, but taking into account his whole kit, MUs, and mobility, I believe him to be a low high tier character now.
are a-okay, but Sonic's were just stupid to me. For Glory warriors, thanks a lot 
)