The remaining tanks, Zarya and Winston, may work in tandem with two attackers, Genji and Tracer, to bring about a revival of a composition that has existed before: The Dive composition.
The Dive comp works by exploiting its stack of high mobility heroes. A typical dive comp works like this: The dive comp team waits until one or more of its ultimates are charged, then Genji, Tracer, and Winston “dive” onto the backline of the enemy team, targeting the weaker heroes (particularly supports). The assault, first of all, causes mayhem. Genji and Tracer are highly mobile, and the tanks in the frontline now have to make a decision: turn around to help their supports and risk being taken out by the Zarya that they just turned their backs to, or stay facing the Zarya and risk losing the weaker members of their team that are currently fighting Genji, Tracer, and Winston.
If the defending team chooses the former option, the dive comp has even more tricks up its sleeve. As soon as Genji, Tracer, or Winston take too much damage, Zarya can hit them with a projected barrier to both give her more energy to do more damage and allow the bubbled ally to escape the fight to get healed. If the defending team chooses the latter option, they are essentially choosing to spend an important support ultimate: because the supports and weaker heroes are at a disadvantage facing a tank (Winston), and two highly mobile, burst-damage attackers (Genji and Tracer), the chance of them winning is pretty slim. They usually have no choice but to burn a support ult (usually Sound Barrier or Transcendence), which charges more slowly than the ults of the two attackers they are up against. This means that while they might win that team-fight, they will be at a disadvantage for the next one because they won’t have their ultimate yet.
The Dive comp also has some interesting options when it comes to supports. It could use Lucio and speed boost to make the already fast-moving flankers even harder to hit and allow them to more easily escape when they are hurt. It could use Zenyatta to allow for more damage output from the side of Zarya as well as healing for one of the flankers in the backline. It could even opt for a Mercy to damage boost the Zarya and revive the backline attackers, essentially giving them two chances to take out the enemy team’s weaker members.
The Dive comp hasn’t functioned very well during the current meta primarily due to Ana. Her ability to heal essentially her whole team in a burst manner with Biotic grenade, along with her extraordinary ability to defend herself (Winston is a pretty easy target to hit with sleep dart) usually led to too much sustainability for the diving attackers to overcome. Now that both she and D.Va have been toned down, the Dive comp may have the damage output to be viable once again.
But, even if the Dive comp fails, there is another threat to the tank meta on the horizon. Developers on the Battle.net forums have been teasing lately the current experimentations being done internally with Bastion. According to their posts Blizzard’s goal is to transform Bastion into a true tank-buster. Their current plan for accomplishing this is to remove his headshot capability while in turret-mode, but to then give him in some way either greater health or higher defenses. This means that smaller characters like Tracer, Solder, Genji, and many others won’t have to worry about Bastion melting them at mid-long range, but larger targets like the tanks will have to respect Bastion’s damage output or risk taking massive damage.
It hasn’t been announced yet what the specific changes will be and when they will hit the PTR servers, but I think it’s safe to say that one way or another the meta will be shifting from the current tank-heavy meta during the next month or so. It may move to the dive comp, or we may see entirely new comps arise with the changes being made to Bastion. Right now, with all of the changes being both made and previewed, it might be time to start experimenting. Who knows what crazy hero composition may find itself the new Overwatch meta?