No matter the situation, thinking clearly will help you. This is especially true when dealing with the "plague of quick match" Bastion. Approaching every situation from different angles will help you stay ahead of your opponents and score a victory with your friends and teammates.
You can change your hero at any point in the match, this is a very powerful tool you can use to single handlely change the outcome of matches. Overwatch is much different than popular FPS's through its use of Heroes, but differs from MOBA's like HotS, DotA, or LoL because you switch any time you die or are in the respawn area.
Changing your hero can mute one or possibly two hero choices from the other team. Imagine you are a playing a very strong Widowmaker: Two players switch to Tracer and Reaper to counter your Widowmaker. As soon as you notice this, or die because of it, switch to McCree for instance. In this case he counters both these heroes well.
Using hero switching well can not only negate the enemy picks, but open up the heroes you play best. Starting as say McCree again to deter the use of heroes that counter your Widowmaker giving you freedom to use her. Be aware of counters and use them to your advantage.
Be aware of what hero brings when you switch, leaving your team without a critical role or hero will hurt your team. If you are one of those critical heroes and your team is need of a change up, considering looking at similar heroes with slightly different abilities (i.e If you are Reinhardt, Consider Winston if your team needs a more mobility rather than Tracer or Genji).
Offer different answers to problems, both through varying play-styles within roles or heroes, and switching effectively. When you adapt to flow better than your opponent's you will be dictating it, consistently keeping them on the back foot.
In all team games the group that sticks together and works as unit has better chances. Teams who fight 2v5's, 3v6's or even go in alone, will start a "Pick-train" for the enemy that will eat up time your team needs for pushing or holding the point/pay-load. This will make it harder to mount a meaningful effort as a team when everyone is dead or separated. Always take the time to find your team and group up with them (if your playing a hero like tracer, reaper, etc. there are exceptions to this).
Exploit teams who have players that take fights alone or in lesser numbers. When you are able to start picking off players 1 by 1, 2 by 2 you gain a great amount of tempo and can translate this to objective time. Find the players that are pushing too far, or playing with too much adrenaline/emotion and kill them first every time. This is the easiest way to start the "Pick-Train."
Abilities have Cooldowns, be aware of your heroes cooldowns and what situations they excel in. Refrain from using the logic, "I do not wish use X ability because X ability may be needed later" If you never use an ability in the time it would be off cooldown you effectively wasted an use of it. However be wary of using abilities you will later; spamming some abilities will be less effective than if precisely timed. Key point here too is when you feel you are going to die never just run; Juke, shoot, spam your abilities. This will help your team win critical fights.
Synchronizing abilities has devastating effect A well timed ultimate can outright win a game. Know the heroes you are with and what synergies you can exploit. Key examples here is Zarya's Ultimate, which acts as an AoE Vacuum crowd control ability, and Pharahs ultimate, which rains an onslaught of rockets at your foes. If these two ultimates are used in tandem your enemies will have to figure things out back at the respawn area. Here is a list of strong combinations to use in your games.
Overwatch is a team game, and much like fighting as a team with using numbers to our advantage, we want to synergize our abilities, pushes, and picks. Think and work as a 6 man team, communicate with any force you wish. I found during the beta the emotes were particularly useful (especially the one letting your team know the status of your ultimate).
Compiled spreadsheet of discussions I have had with some pro players, forum discussions, discussions I could find, and personal theory-crafting. It is currently in the second major iteration and will be updated after more professional matches have been played. If you have any thoughts or comments on this spreadsheet you can leave them as comments there or here.
Tl;DR: List of strong hero synergies to use matches with friends and teammates. Examples of strong hero synergies are Zarya + Damage Ultimates (i.e. Pharah's Barrage, Reapers DeathBlossom, Hanzo's DragonStrike). Example of strong hero Combo: Pharah and Mercy pair uniquely well; Mercy can pseudo-fly by sticking with Pharah, and the Damage Amplification makes Pharah deal 156 Damage with direct rockets. Strong Team Compositions, Protect the President utilizes Bastion setting up on the Pay-load with 2 Reinhardts using barrier to shield him. A Mercy to Amp the Bastion, and heal the team. 2 Widowmakers, who cover the Bastion and Reinhardts and if ignored deal amazing burst damage.
If you are looking for more advanced content than what is above this series is for you. Each episode will dissect a professional team composition or strategy so advanced players can execute it better, and newer players can learn about them.
Summary: Cloud 9 unveils the first competitive variation of a Bastion based composition. Using Bastion on the pay load with 2 Reinhardts, and Mercy to immediately assist him - add 2 Widowmakers and this line-up can dominate any escort or hybrid map-type. Because Bastion has so much room with 2 Barriers protecting him and damage amp, coupled with the 2 Widowmakers and 2 Reinhardts being a threat in their own right; this comp has to be dealt with cleanly and swiftly.
Summary: Double McCree, Double Lucio, Double Reinhardt, used by EnvyUs on KoTH map type versus Luminosity in Overkill.GG for 3rd place. This strategy uses aggression to seize tempo and cap the point, push out and establish a soft contain to get extra objective time. Through sticking together as 6 heroes and having healing and speed auras this lineup can be terrifying to play against. (McCree's can be subbed for tracers, and Reinhardts for Winstons).
Summary: This episode we will finally cover a Defensive strategy by Reunited against Cloud9 in the Overkill.GG Finals. Using spam, position and information manipulation Reunited's strong individual play lets them take the map, and tie the series.
Summary: This episode will be covering the elephant in the room, can individuals shape the outcome of the game? In this match between Luminosity and EnvyUs, Seagull and Enigma prove how much value there is in strong individual plays. Without their abilities in this game, Luminosity would have lost.
Thank you for reading this! I hope any of it helps! If you have any discussion points or thoughts please let me know!