This is a huge part of the game being fun. Some people relate this to doing damage as opposed to support, but as long as you feel like you really added to the team you probably had fun.
There are plenty of times when a hero doesn't work out in a single game. The first time my roommate played AZ he kept having gear bounced and all kinds of trouble. In the last turn of the game he did something like 2 damage which was all the damage he did for the game. He was all "Hey guys look at me! I did damage!" to which the other heros gave him a golf clap and a pat on the head. Well, I told him to try again and in a later game AZ was the amazing MVP of the show. My roommate didn't even play him that differently, he just got what he needed and nothing was screwing with his setup. This has been AZ for us, very hit or miss. End result, we like him and know this about him going into the game. Even when he has a bad game it becomes a running joke. We don't consider him weak but might say he is inconsistent or has certain horrible matchups.
Expat on the other hand has never had a 2 damage game for us. She always contributes some but it feels like she never contributes as much as the others (Unless AZ is stuck in a box or something). Maybe, as some have suggested, this is because her damage is kind of spread out and not fancy. But we have tracked damage on her recently (though its a small sample size) and the numbers aren't good (For us). Part of the reason is we don't play with Legacy much to galvanize, part of the reason is we seem to never hit Hair Trigger Reflexes until late game or the boss doesn't have lots of targets. Besides this she doesn't really contribute in other, non-damage ways (except RPG maybe). The final result is we don't feel like she contributes as much as the other heros and that leads to being less fun to play. I really like her flavor but I notice her being left in the box more than any other hero.