On the flipside for people who limit themselves to viable tank heroes they get to play a wider range of playstyles.
All of which are geared towards being more Fun.
I don’t really care about purely theoretical variety.
I’m a GM support player and I couldn’t disagree more. I think that 5v5 is what is going to be the saving grace for the game. Please also consider that most of the support heros are not functioned to be heal bots. Also, a huge point I see a lot of people miss in their discussions for 5v5 is that, fundamentally, very nearly every hero will get some form of rework to fit in the confines of 5v5.
We see a lot of discussion about the tanks, of course…but people seem to be viewing that in a bubble. Even just considering tanks; every tank is getting beefed up in some capacity to make up for having just one. So the idea that ‘Oh, there is only one tank, who will peel for the support’ is only being viewed as if one tank from OW1 is missing and that is the only change to the game. That’s obviously not the case. A front line ‘brawler’ tank will have more in their kit -take Rein, who has mode damage and maneuverability- to help out, rather than just having to sit in a choke with a shield up.
You seem to also be missing the idea that all the roles are getting new passives. The tanks are getting a form of steadfast and diminished ult charge (which favors support ults over DPS ults then, realize). The DPS will all gain a movement speed buff -which also will tremendously help with conceptual peel-, and the supports all are getting a HoT similar to Mercy’s. That’s tremendous.
It goes without saying that any support has to be able to exist in the face of a dive. If you are playing support and just outright collapse every time you are dove, you will drop SR because you will lose. The support heros are all strong, and all of them have a viable way of dealing with or mitigating dives. Peel is for something even extra beyond that. So if you can’t preform on your support hero, you will go down in SR, rightfully so.
But even consider the minutia of the rebalances that have to go on in the support role; a hero like Mercy, who is stronger the less she has to focus on a group, and then consider 30s rez on the all-important solo-tank, will feel dominant. Then look at Lucio, who is stronger in groups and is a support intended to work well with tanks, and he will feel weaker. That alone will show what sort of scope rebalances need to look like. Who is to say that each support’s survivability is not brushed up in some way?
Though, to be fair, they don’t need to be. If you’re playing support and dying to dives all the time without peel…you’re not playing the hero well, tbh. You don’t have to win the 1v1 with Tracer or Doom or Winston all the time, but you certainly have the tools to survive it or get them to leave.
I don’t see how equalizing Tank kits will make the Tank experience more fun.
Also it is not “theoretical” variety that is getting lost.
Sure, there is a meta… but 5v5 won’t change that.
What will change is, that everything goes a faster paced Team Deathmatch playstyle - and if I would have wanted that, I would be playing a different game.
For some reason they are trying to appease the FPS crowd, but is it really realistic to expect people who prefer the FPS playstyle to switch from CS:GO & Co to OW2 as their main game? 
The reality is that %90+ of the high tier tank pickrate experience is whatever it meta, which is usually limited to 2-3 Tanks.
And 60% or more of the Plat and below pickrate experience is Rein/Zarya, with another 20% as Hog.
That’s a lot less “real” variety than you think it is.
As if Hog/Zarya and Ana/Bap don’t have anything to do with FPS playstyles.
A lot more realistic than expecting to recruit WoW and LoL players into a game that’s primarily a shooter.
Especially when OW2 PVE is surely going to drain a significant portion of those “don’t go for kills and just focus on heals and blocking damage” players.
Especially with the bizarre audacity to assume somehow those “non-aggressive” players will outnumber kill focused players.
It’s not as if the Rein/Zarya issue in lower ranks wouldn’t be fixable if they actually were willing to put some work into it.
Besides that the balance seems to be very good especially at higher ranks.
In GM the pickrates range from 8.5% to 17.5% while half of the Tanks are sitting pretty much exactly at the sweet spot of 12-13%.
As long as you coordinate it with your teammates, you can play any Tank you want.
I can’t believe the in-development game isn’t balanced properly yet 
Shaking and crying rn tbh
Kinda don’t care if tanking was magically perfect for 5% of the players, if it sucks for the other 95%.
But even for that 5% it’s just a matter of time before the meta hardens and tank choices shrink dramatically.
I have never played multiplayer shooters before Overwatch.
Before I mostly played RPGs/MMORPGs and RTS and I gave Overwatch a try exactly because it sold itself as “different” with a higher variety of playstyles.
And you would rather risk breaking the entire game while turning it upside down instead of simply fixing Rein/Zarya?
The thing is there is no simple answer.
And even to the extent they could balance pickrates, that’s not the same thing as moving tanks closer to the popularity of the DPS role.
Making changes to Rein and Zarya is arguably much easier than having to at least partially rework the entire Hero roster.
You aren’t going to fix a Tank shortage by alienating your Tank player base.
DPS Mains and new people who come from other FPS aren’t going to play them - no matter what.
That’s nice, but the idea that these sorts of players would make up 66% of the playerbase is ridiculous.
Realistically these sorts of players make up maybe 5% of the total playerbase. Maybe 10% of you’re really stretching it.
It’s not worth screwing over 90%-to-95% to chase after such a small minority group.
More like less than a sixth of the tank playerbase, which is maybe 15% of the total playerbase.
15%/6 = 2.5%
Don’t think the devs are gonna lose sleep about the financial impact of losing a fraction of those 2.5% of players.
You really really overestimate the scale of these “Non-aggressive” tank players.
I want them to run away from Orisa in 1v1 situations.
Orisa, “Come at me bro.”
I am pretty sure that there are a lot of DPS players who prefer the different playstyle as well.
They have plenty other “more FPS-y” options, but they chose Overwatch and are willing to wait in queue. If that wouldn’t be they case, they would play a different game.
The very moment they turn Overwatch into something that is much closer to one of those games they aren’t playing, is the moment they will lose those players - while not really getting anything in return.
Overwatch can’t win if it tries to compete in the “true shooter niche”.
Oh well, all is good as long as they gain more players than they lose.
You literally can’t please everybody, so they should focus on making the most players happy.
Not the fewest.
And that’s exactly why 5v5 makes no sense at all.
If you compare Role Q and Open Q, Open Q is much heavier leaning towards the FPS playstyle and has much shorter Q times for DPS players.
But which of the both modes do you think most players prefer?
While we lose a tank the supports are unfortunately going to be under the most pressure due to what OP mentioned… Plus we don’t know how they plan on changing every hero (what they showed wasn’t a finished product obviously)
I said this in another 5V5 thread… but not many people actually read (I don’t think)
I play support because I have fun healing and supporting my team and am not one bit excited for the game to be changed to 5v5. One less teammate means I have one less player to help so it’s very hard to imagine this change as an upgrade.
They should just add in a big team mode with 7v7 or something; adding a dps slot.
Both 5v5 and 7v7 should exist just like how we have open-que and role-que.
Another spot on assessment from almost 9 months ago.
How do these users keep predicting the future?
Oh, that’s right, we have 6 years of both player and dev experience to draw from.