The biggest appeal and criticism professional players had since Overwatch's closed beta was that teams were able to stack duplicate heroes onto the same team. The "no hero limit" was what defined the Overwatch meta for seven months straight, bringing in the Double Orb composition which utilized two Zenyattas and Double Winstons. Other than that, it was standard for two Lucios to be run on King of the Hill maps and two Reinhardts on payload maps.
With a lot more time put into weekly tournaments at Gosugamers, it became clear that certain rules had to be implemented when looking toward the longevity of the competitive scene. Hero diversity was incredibly low and the meta was stagnant.
Eventually, Gosugamers listened to the criticisms of several professional players, who recommended that tournaments ban all two-capture point maps, implement the True Stopwatch rule, and follow the one hero limit. From that point on, the value of the new system shone but it also revealed potential problems that left people asking for a return to the former rule set. While there will always be dissenters, the one hero limit is the clear-cut choice for moving forward in the Overwatch scene.
The early benefits of the wild, wild west
For several months, the competitive scene in Overwatch thrived without restrictions, bringing games of great entertainment value. When Gosugamers started the trend of limiting each competing team under the one hero limit, team composition diversity went down. Team comps on almost all maps became staple and "solved." If you looked at certain choke points, the best defenders boiled down to having both a Symmetra and a Junkrat. Under the one hero limit, that became a very difficult fight to traverse.
The solution to these types of compositions was to employ non-conventional strategies such as Double Winston. Using a Double Winston in this situation means that both tanks can jump over the long stretch or a wall of the choke-point and immediately single out both the Junkrat and Symmetra while dropping portable shields to run through with the payload.
The reason there wasn't immediately a lot of innovation room under the one hero limit is because there simply aren't enough heroes yet. With 22 characters, teams are only choosing around 28 percent of the pool. But with Mercy, Lucio, Reinhardt, and McCree being picked more than 70-80 percent of the time after the one hero limit was first introduced, there was little room to employ other creative hero solutions to existing comps.
The biggest reason to keep the possibility open for stacking heroes lies in the strengths of certain heroes. Heroes like Tracer, Reinhardt, and Lucio are extremely potent in what their kit aims to do. But having two of them on the same team doesn't just double its effectiveness, it multiplies it. Double Lucio is mandatory on King of the Hill maps for stacking healing auras. Double Reinhardt means they can trade off shield uptime or provide a bigger cover for their double Widowmakers and Bastion.
After a few weeks of the one hero limit being implemented, Tracer was being picked roughly 30-40 percent of the time. However, ESL joined the Overwatch scene and lifted the one hero limit format for their tournament. As a result, Tracer was used in pairs on both teams almost every single King of the Hill map.
Almost inevitably, Tracer fell back down to a sub-25 percent usage rate when tournament formats returned to the one hero limit.
Unique heroes are the future
The one hero limit needs some working out for the future of the scene but there is a lot of evidence that points to this rule as the standard for all future Overwatch tournaments. Over the course of several weeks and hundreds of games, there is one undeniable truth about the one hero limit: it has raised hero diversity. Compositions are now not being forced to use two of the same heroes, specifically Lucio, McCree, and Reinhardt.
There are a lot of map-specific heroes being picked now such as Junkrat and Symmetra. Don't get the wrong idea though, Symmetra is still a very unpopular hero but she has a very specific niche on very specific maps. Another surprising example was Zarya's sudden boost in popularity when playing on offense. Not being able to stack Winstons in a composition meant Zarya could be played, providing a shield for in-your-face offensive heroes like Reaper.
While the theory that the one hero limit would kill a lot of the creativity of stacking comps, pros would soon realize the domino effect the limit would cause. When being forced to use a specific hero, another hero will rise in popularity to either counter it or to synergize with it. Zarya's popularity on offense brought out a resurgence of Pharah. Widowmaker and McCree's nerf helped bring out a resurgence of Soldier 76 and Roadhog.
McCree's nerf also brought about a surprising combo used on some payload maps that utilized either Soldier 76 and Roadhog. This itself demonstrates a sort of self-solving problem when it comes to metas in competitive esports. This effect has long been demonstrated in League of Legends, where one champion's rise or fall directly affects another champion's popularity.
Blizzard can't always justify a nerf to a hero just because two of them on the same composition can break the meta. It didn't do that before and it would cripple a hero individually when their only power imbalance is brought about with the no hero limit. McCree was used in pairs all the time, but even on his own he was the king of DPS (damage per second) with the hardest counter to Tracer and Pharah. This allows Blizzard to safely and healthily buff and nerf heroes without the risk of letting two to four of the same hero overtake the meta.
Over the horizon
While Gosugamers' weekly tournaments in North America and Europe set the precedent for the one hero limit, Blizzard has since endorsed the rule in competitive play by implementing the same rules in-game for competitive mode. It's safe to assume BlizzCon will likely enforce this trend and show a ripple effect across the rest of the competitive plane.
In the youth of the OW competitive scene, there were a lot of downsides to having the one hero limit. Gone are the days of seeing the D.Va spam defense, and the Crossfire Defense in Watchpoint: Gibraltar can only be executed in Free Play now. There is so much innovation to be explored under the one hero limit and the only thing holding it back is the lack of a bigger hero pool. Being able to stack heroes is fun and creative but it's important to administer restrictions so the competitive scene doesn't spiral out of control.