If you are loosing attacking your team isn't diversified and you have too many solo players. Attacking is won by sticking together sans maybe a player or two. Solid tank + Healer can walk most payloads in. Most check points you can capture if you clear the entire defense. They won't ever reach the point after respawn, usually setting them up to be disjointed on the second point and needing to turtle hard on third point.
Bastion could use a little more spread drop off, but that is about it for him, having problems with him otherwise is you needing to know the map and someone countering him. If he's getting play of the game repeatedly or being the best your team is walking into overt death traps or the Bastion is actually a good player.
Widow's secondary could probably use some knock off to be a little more inline with Hanzo as his arrows don't carry the same punch as her sniper rifle/full auto weapon. But I wouldn't be bothered if they didn't change as they can be countered.
The game is far from perfect, but very fun. The game relies on solid team strategy to be dominate and I'm hope ranked play livens it up a little bit. Sometimes in character select screen alone I can tell if we are going to win or loose based on character choice + Map + objective.