Did they actually try to counter you? A quick Genji or Junkrat pick should have easily stemmed the tide. The fact that they "couldn't do shit" against one character tells me that in fact your opponents were not that great or that the rest of your team was that good.
Like I said, he's not a top tier character. He's a fun pub stomper. Not much more.
I'm not the person who originally posted, but I've been playing Tjorb too, and you can do relatively well with Tjorb against even decent players because 99% Tjorb's are playing like TF2 pub engies who sit behind turret in one spot and keep hammering it.
Perhaps the person is playing Tjorb right ie: Putting up a turret and leaving it there while flanking/rushing the enemy with the turret backing up your 275 HP armored body. Frequent turret placement changes and molten core during pushes can easily confuse and stomp even decent players.
Tjorb is good at many MMRs, just not that great at the scrim/tourney level it seems like. Seagull's been using him in pubs with success.
IMO Hanzo/Widows shit on Tjorb and Bastion but if you're smart as Tjorb you can manage to not pigeonhole yourself into one corner and keep getting your turret 2-shotted.