Hey dude, been playing Greninja for a while, not as long as you mind, but I'm pretty happy with how the deck runs, for the most part. I do have a few questions/suggestions to make, however.
I play 7 Basics in my build. and I still find that I can get stuck mulliganing a few times before I have starter. I know N is in the format, which makes this less problematic in terms of giving your opponent extra resources, but I don't imagine opening N happens all that often in your build. I think running FF Dedenne can be really clutch in games where you open next to no Froakie.
I've tested running the one-of Greninja XY 41, and while being able to put the extra 30 damage on board can be useful, particularly if you have any BREAKs prized, I feel it's Breakpoint counterpart simply outclasses it 9 times out of 10.
Regarding the Ball discussion; 1 Ultra Ball, and 1 Level Ball seem fine, but I would still run the 4th Dive Ball. WastedSkyPirate also suggested running Sacred Ash over Super Rod, and I have actually tested two of the former, but found that in some situations I'd open with it and a Sycamore early game, resulting in not gaining anything from the card, whereas even being able to shuffle back in some Water Energy before a Sycamore can be beneficial. I ended up replacing them with two Super Rod, because sometimes you do need to recycle some of your Greninja lines.
I don't really see how you get enough value out of playing one Battle Compressor, let alone two, to me it's a waste of a VS Seeker, if that's all you're going for. I would rather Skyla into the Supporter I need, and wait a turn. Rare Candy is another one, especially considering you're not maxing out on Froakie, but even then, it doesn't seem necessary with Water Duplicates. AZ seems a bit strange, too, but I get what you're going for, I'm not sure I'd be able to find room for that one.
As for Mirror Match techs, I find Hex Maniac really good, as it makes you less reliant on using Stitching each turn, increasing your damage output. Trainer's Mail could be a good alternative to the Battle Compressors too.