You serious bro?Only if it runs sub par sets. In order to beat Chansey and Empoleon it'll have to run a lot of attack investment. In order to beat Keldeo and Tentacruel it'll have to run Extrasensory which isn't an ideal move for ninja because of its 4MSS. You are ignoring the opportunity cost in running these sub par sets. And thanks for ignoring the rest of the argument that Ninja's overall influence on the metagame is not unhealthy since the same teams are showing up again and again on the OU suspect ladder.
Greninja takes full advantage of it's "4mss" because Ninja picks it's targets based what it's team hates the most. So to clarify here: Greninja picks it's checks and counters, not the opponents. Meaning they are forced to be overly prepared for Greninja or just get lucky it doesn't happen to have hp fire, extrasensory or something to screw your best check. With that in mind you are only counting Greninja will only run it's standard set while that is purely optimal because it's all attacks are STAB it loses nothing to change it's coverage. You cannot say you got Greninja covered just by slapping Tentacruel on your team just because you don't expect it to run extrasensory when it is a very viable option and when it does it screws your entire team over. Because you can't use type advantage against Ninja virtually only handful can call themselves counters to Greninja and all of them are too passive to be on anything but stall teams.
This goes for all anti-banners: I implore you to read the Victory Road version because they have summed up the problems Greninja brings to the metagame better than I could ever hope and I am just seeing the same anti-ban arguments being beaten down over and over again and I want to see if someone can say Greninja is not a problem and have a explanation how Greninja can be reasonably handled without just using the same mons on all teams.
http://www.smogon.com/forums/thread...round-1-teenage-mutant-ninja-turtles.3525052/