I'd like to give my honest thoughts on Darkrai as a 'mon right now. It was a while back where there was a lot of about dropping Darkrai, with great
posts from
Vert and Mimikyu Stardust. Initially I had thought these posts were pretty far-fetched; the same special attack stat as flutter mane whilst speed tying with Weaville does not seem balanced at first glance, however after being part of the vanguard for my OUPL team with cooking up teambuilding ideas for the OU Suspect Tier in OUPL, as well as witnessing games with Darkrai played during OUPL, and having discussions with other players about Darkrai, I believe Darkrai would be fine for the tier, and should be considered for a drop when DLC2 comes around.
My biggest issue with Darkrai is its frankly atrocious single-typing, which is not amazing defensive or offensively.
Some people in this thread have compared Darkrai to Iron Bundle or Spectrier, which I believe is very crazy, considering the fact that Iron Bundle's Water/Ice coverage has no resistances, and Spectrier's Ghost type STAB Shadow Balls are very spammable, with a super high speed stat too, as well as gaining access to powerful Draining Kisses and being able to Tera and Tera Blast for extra coverage and a better typing. The former offers much better utility than Darkrai as well, having fast encore as well as Flip Turn, a great pivot move, making Iron Bundle not only great offensively but also being able to keep up momentum and stop sweeps instantly, complemented well by its fast speed.
Darkrai, unlike Iron Bundle, also has a useless ability of Bad Dreams, which is only good after you hit the 60% Hypnosis. As the person who made Hypnosis Ival get spammed on the ladder when DLC1 came out, I must say that I used that set only as a way to flip matchups when they are
already lost (such as Amoongus, Toxapex, Glowking, Heatran etc.) whilst having a chance to get a positive gain from them (getting CM and potentially breaking through the aforementioned threats) without having to lose momentum by switching out and wasting the booster energy. Darkrai on the other hand has terrible 4mss - if you choose to run Hypnosis, you are forced to run Nasty Plot or else you will do 0 damage whatsoever due to Darkrai's main stab move of Dark Pulse being resisted by 50% of the tier's offenses. It's final moveslot will have to be sludge bomb so you have a reliable way to hit fairies, however that leaves you being vulnerable to Kingambit, Ting-Lu, Great Tusk, and the myriad of other resists. Either that or you run something like Focus Blast and get shit on by Fairies; its a similar situation to Iron Valiant and Gholdengo however the difference is that Iron Valiant has access to Booster Energy, which lets you revenge kill pretty much everything with its great typing and movepool; something Darkrai is unlikely to do despite its expansive movepool.
In that case, let's check out the scenario where you just accept Darkrai's ability to be trash and use NP with 3 attacks, Dark Pulse, Sludge, Focus Blast. Here players will be lead to the next point of concern; Darkrai's mediocre bulk. The best answer to Darkrai will frankly be priority - something that every team by now should have, whether it be a Rillaboom Grassy Glide, Dnite Espeed, Scizor BP, Gambit sucker etc. If Darkrai was to be released, the player base will pretty quickly adapt and put reliable revenge killing on each team - not like this isn't already the case, with Iron Moth, Iron Valiant, Booster Tusk, Scarf Enam etc. It feels so weird to say this, but Darkrai's speed is frankly not on par with real sweepers, which are well over the 500s, and it doesn't help that it has a terrible typing that makes it lose to literally everything else offensively as well.
I have been seeing many walls of calcs but they are all with life orb - which shows that even at +2 it needs to utilise an offensive boosting item to make the best use of its offenses and high speed, which puts you at a disadvantage by not using boots, and completely folding to the hazard metagame. This is of course not taking into account mons faster than Darkrai, such as Dragapult and Zamazenta, being able to revenge kill it too without expending an item, the latter definitely being one of the better checks thanks to its dark resistance.
Darkrai dropping would not completely overwhelm the metagame to a point where it collapses on itself, such as what happened to Blood Moon. Darkrai's introduction to the SVOU metagame would see it be a potent balance/fat counter with NP and Taunt, as well as being a solid mon in general. It would also have heaps of counterplay, such as lack of recovery leading to chip wearing it down, priority moves overwhelming it due to its lacklustre defenses, 4MSS, no ability unless you want to fish for luck, too slow for the booster energy offensive mons etc.
There has also been some mentions of choiced sets, such as Specs or Scarf. I truly believe these are utterly trash seeing how bad Dark is as a type to spam, and being locked into a move on a mon especially like Darkrai would be detrimental, although I would see Scarf having a niche. On top of this, I have seen people who say "Darkrai has been Ubers forever why drop it now", maybe this is a clear sign of Gamefreak's power creep - this is not a valid argument imo.
As someone constantly searching for new ideas and seeking for creative teambuilding, I do think Darkrai dropping would add value to the OU metagame, being a niche answer to Balance and Fat whilst having plenty of counterplay, like I mentioned above. Needing to utilise a Life Orb for maximum damage is also not great, as Darkrai would fit heaps better with a boots set, leading it to miss out on important 1HKOs at +2 that would be achieved with a LO, at the expense of succumbing to the common hazard-stack archetype. Respectfully, comparing it to Iron Bundle really isn't helpful considering the insane difference between the two. At least Iron Bundle has good defensive bulk, letting it live Espeeds and Sucker Punches. Looking forward to Annihilape and Giritina-O week - those mons are what is considered too much for OU, not Darkrai.