Deoxys-N is probably uber, being a miniature Deoxys-A, but I haven't seen it at all.
If you haven't seen it at all, you probably shouldn't judge it. Deoxys-N is high risk/low reward compared to other sweepers IMO. Yes, its offenses may look high, but keep in mind that it
has to run a Speed-boosting nature. He needs this to get the jump on some of the slower Scarf users or Swift Swimmers that will completely bone him otherwise. This means that he's only reaching 399 max in
one attacking stat. When he can't even boost his attacking stats outside of Calm Mind, he really has to rely on super-effective hits to get kills, especially if he tries going mixed. That, and with all of the power creep this gen, is 399
really that high? With all the Rain sweepers and new Sandstorm sweepers hitting just as, if not, harder, with the massive BP on their attacks, or in Doryuuzu, his higher Attack stat, 399 Special Attack is pretty manageable.
Unfortunately, these don't even hit hard enough, especially against walls, particularly those with reliable recovery. For instance, a Superpower coming off of 399 Attack with a Life Orb is only doing a max of 83% to Evo Stone Chansey. This means that if she comes in on a Special Attack, she still has a good chance of winning. Realistically, Deoxys-N isn't going to be using this spread if he wants super-effective coverage, because most of that comes from his Special movepool. So more realistically, it'll be coming off of 336 Attack. This can do an absolute max of 70%, most likely lower. Chansey can stall that out with Wish/Protect if she comes in on a Special attack.
Furthermore, just like Deoxys-A, Deoxys-N has horrible 4-moveslot-syndrome. He needs to have the moveset Thunderbolt/Ice Beam/Psycho Boost/Psychic/Superpower/ExtremeSpeed/HP Fire/Shadow Ball/Substitute, but unfortunately, he just can't run all of these at once. It's even worse with Deoxys-N, because he actually needs all the coverage he can get if he actually wants to kill things.
Basically, he's screwed by any Steel not weak to Fighting if he doesn't run HP Fire. Bulky Fighters will wreck him if he doesn't have Psychic/Psycho Boost. Bulky Waters ruin him if he doesn't have Thunderbolt. Dragons will have a much easier time if he doesn't run Ice Beam. Without Superpower, he has nothing against Tyranitar, Chansey, Blissey, and stuff like Heatran. Without ExtremeSpeed or Substitute, he can't protect himself against priority. And without Shadow Ball, many Psychic-types will have lots of fun against him. It's also unfortunate that Psycho Boost is the only attack here that has high BP running off of his more important attacking stat. We've all seen cases like Electivire where they have high attacking stats, but the BP on all their moves blow, and as a result, they get walled to hell by a lot of threats.
In addition to all of this, something on your team has to die just so he can come in, because there's no way in hell that he can actually switch himself in with those defenses and actually hope to accomplish anything. This is a key part in me saying that he's high risk/low reward, because honestly, if something has to die for my sweeper to come in, they sure as hell better be reliable at doing their job, because it's going to be really difficult to bring them in again if they screw up. Unfortunately, Deoxys is quite unreliable in this aspect, because if a Choice Scarfer or Scizor comes in on one of his attacks, what's he really going to do to them? His ExtremeSpeed isn't strong enough to even 2HKO Garchomp even if he carries max Attack, and with min Attack, it can't even 2HKO 0/0 Rotom-A, both of which can destroy him.
At least with something that can boost their stats like SD Lucario, their attacks will be strong enough to take out walls, and if they have priority, hopefully take out faster pokemon. But since Deoxys-N can't boost his stats without relying on CM, which he'll have a lot of trouble setting up, since most people will just attack Deoxys-N right off the bat, he can't really do this.
Honestly, Deoxys-N doesn't impress me at all, and it's really, really confusing me as to why people think it should be a suspect when 1) Deoxys-A is still here, and 2) it's really not an easy pokemon to use well.
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On another note, I've been trying out Specs Shaymin-S + Wish Chansey. It's an absolutely monstrous combination, since Shaymin-S with Choice Specs on can break through most of its counters, and Chansey fully heals Shaymin-S with Wish, removing any Stealth Rock damage or other damage, letting Shaymin-S do its job again and again. It's also nice that Shaymin-S resists Chansey's one weakness, so if, for instance, a Roopushin comes in while Chansey uses Wish (which happens a lot), just send out Shaymin-S to take the Drain Punch, and you'll not only be a full health, but Roopushin will also be in a lot of trouble, while you put shitloads of pressure on the opponent. Air Slash is actually really powerful with Specs, since it can actually OHKO a lot of sweepers, and Specs Seed Flare is the reason why I recommend people try Chansey over Blissey, because Seed Flare has an 80% chance of 2HKOing Blissey if both of them hit. I personally find this set to be way better than Scarfmin-s, because that set doesn't really hit hard enough and still unfortunately can't outspeed Doryuuzu even with Timid. I'm not going to say whether the set is broken or not, but leave that up to yourselves when you try it out.