Against stall, how does one evaluate strategic sacrifices, such as whether trading a Special Sweeper for a Special Wall. Well, that would not seem to be an advantageous trade off if that is your only special attacker, but if that is their only Special Wall and you have another Special attack then it is a nice trade off.
How can Conkeldurr be an excellent core breaker, given its weakness to inefficacy against Fairy and its low speed, which is detrimental against walls with access to recovery? Who should it be teamed up with to assist its performance against stall. Its main partner is Klefki who can give me quick paralysis without prediction (against Sub users who may try to thwart it), but this is less effective against stall since they usually have clerics to mitigate the protracted effects of paralysis in the free turns that it might generate.
How important are hazard removal and clerics for bulky offensive against stall in relieving defensive pressure, even for a team with no Stealth Rock weakness, although stall teams are less likely to use Spikes now?
Should I alter my playing style as I describe it as a conservative tactical style involving creating what I perceive to be favorable match-ups and exchanges and achieving a small gain for each turn and it is less prediction intensive than other offensive styles which involve making high-risk/high-reward decisions (I do not use Choice items). Do stall tactics have a natural advantage against conservative offensive players?
Deception seems to be necessary. Landing an Ice Beam on a Gliscor with an Expert Belt Genesect is so gratifying and saves me a lot of trouble. No need to rely on Hydro Miss from Rotom-W (and it doesn't even KO it anymore :(, what a valuable KO since it obviates additional trial with Hydro Miss)) to break those damn subs. I think EB Genesect will be more powerful and more players would expect it, reducing its valuable.
So, what I would do is at the begining of each match, mentally assign targets to each of your opponent's pokemon. My dreadnought team has a list of all the OU threats that I probably spent three hours writing up a basic outline of what could handle what on my team. It's more a resource for others since I basically have it down pat, but this is basically what happens. If I see talonflame, aegislash, greninja, genesect and rotom wash, I'm assigning slowbro, m-venusaur, chansey, heatran, m-venu/chansey respectively to handle them. Notice how I'm doing this with four pokemon? This means I have three sacrifices worth making if need be. Skarmory will probably be a pinch aegi wall and cofagrigus is some canon fodder for talonflame (generally HP bomb it) at best, so if I need a sacrifice, I have them.
But for bulky offense, they MUST take care of the clerics vs a good stall player. If they don't, it's going to be a tough match that they have very low chance of winning between two fairly even teams. As the turns go on, the stall player and the one used to their team in such long games will have a bigger and bigger advantage. So as a stall player, never give up your cleric until you have victory. If I did a poll, games where your cleric lasted longer than 4 of the other pokemon probably prove to be wins for stall more often than when a cleric gets taken out before 3 others.
But remember that a stall game has a progression of risk/reward pivot moments. Rotom wash in on Heatran, for example. Is it going to pivot or will it hydro pump? I know, from previous experience, I can take one hydro pump from non-specs rotom, so there isn'ta terrible end-all risk, but the reward is I don't have to pivot and I get momentum on the next hit. As you develop an idea for how your opponent plays, find a risk/reward play that might've been fairly high, but your opponent is getting used to the old repetition of the game and just goes through the motions. Once or twice, you need to make a risky play, but make sure you know what each 'risk' means to the game. If mega lucario comes in on heatran, does it SD or CC? Hmm, well I already took care of volcarona, so maybe now it's time to take that risk, right? That's kind of how you judge it.
Just play conservative most of the time. Know your opponent's movesets first.
As for deception, just remember a stall game is going to be so long, eventually the only deception will be on what move you make, not what set you have. Stall cannot gimmick because it intentionally drives out the game to take a more secure path to victory. In that sense, if you're going to have a hidden ace, make it count the first time.
As long as Lucarioite is legal, stall won't be having a ton of success. I got up to 1640 on PO with my build but I can lose to any moron using mega luke who flinches me with dark pulse. It's incredibly frustrating.
That being said, once the meta settles down I think stall will be the most dominant playstyle because of defog. No longer will builds be gimped by having to keep mons like forretress and tentacruel alive to maintain hazard control, and teams can move towards building around status rather than hazards.
Unfortunately, this is simply the truth of it. The physical side is stoppable, there are walls there and the resists of the primary stabs (aka gyarados, slowbro) can take the coverage hits. But on the special side, all of the sudden even if you can take it, you may just get flinched... And most pokes don't switch in, take another hit and then a third and live. In fact, none will.
Until then, however, the main objective is to just resist the two primary hits. and hope for neutral on the third. A relatively difficult job, considering that flying types who do this generally are taking 25% per switch in, and aegislash gets owned by dark pulse. I guess a niche poison type could do the job... Maybe tentacruel? But god does it suck beyond countering lucario... For the months it is legal, I might just make a pokemon on my team dedicated to outspeeding and killing it, but 112 is such a tough speed tier to find stall and usable pokemon to stop lucario. Someone earlier brought up a really niche mega-zam set for stall (but wasn't speed invested so..) and then there is also tornadus-t, which will outspeed should you go jolly and has regerator to help.