I haven't played that much of the Arcade, not because I don't like it but because I just enjoy competitive too much. I do find myself playing some 3v3 or random hero during the off-season though, which sure is fun as well. Haven't tried the new PvE Brawl yet either but I've heard that it's pretty dope too!
I've found myself mostly playing tanks recently, preferably D.Va but I also play Rein or Zarya quite frequently or Winston, when the situation calls for it. I really haven't played much dps this season (can only really play Soldier and Reaper there), but occasionally go healer (every one but Mercy, basically).