I like QP because it's the place where I am actually GOOD with Soldier.
In all seriousness, I should play QP more so I can practice with DPS and tanks. I really enjoy running with healers, but I need more variety. I am barely adequate with anything other than Lucio or Zen (maybe Ana).
I did have a nice Hanzo/Widow run in Mystery Heroes yesterday. Kind of nice actually doing well with a sniper.
I'm hoping for Season 4, I can place a little higher to start (I was around 1650 or so to begin with) so that it might be a little easier to go on a run to gold. Though I fell just short in Season 3 (my first season), maxing just above 1900, I was pleased that I was able to make that much of a recovery after bottoming at 1201 and feel like I played well with my two mains.