Console balancing should cease at accessibility. Characters should not differ from their PC counterparts, at least IMO. Nerfing Torb and Symmetra turret damage is a lazy way to bring these characters on par with their PC counterparts, and in fact makes them worse than their PC counterparts.
Just because Ana requires decent aim doesn't mean she should be void of the nerf stick, if you think she needs it or not. Consoles players have problems with these turrets because they instantly lock on, and you're not going to have the same precision and reaction time on console to destroy them as capably as a PC player. So any nerf to them, should have been to that.
In regards to console balancing, snipers need to be looked at and aim assist could be improved across the board, also fixing whatever other aiming issues persist in the game still. In terms of characters having different stats, HP, or abilities between versions, I don't want this to continue happening for console balance.
In regards to Ana nerfs, I don't get why nerfing her would make her "unusable" on console. If any changes come to her, which they most likely will, maybe even mid-season they need to look into her effectiveness on console as well. I guess going by Blizzard's track record with console balancing, she will definitely be worse overall, but she shouldn't be.
Finally, in regards to the composition itself, three tanks provide a beefy health pool for Ana to build her ult. It is very cheesy and often revolves around tanks abusing the ult system and taking damage on purpose to charge her ult even faster. Ana is not simply rushed down with this comp, with three tanks that act as her protectors one that can one shot most flankers (Roadhog) and Zarya bubbles, Winston/Tracer/Genji have a tough time of focusing her down in the backlines. Doesn't mean it can't be done, but many of teams are positioned in ways where it's hard to really stop her. Oh and she has a handy sleep dart to stop this sort of thing herself.