One of my friends has recently started playing Tahm, and I hate it. He's saved so many enemies by eating our carries to give both himself and the carry a small ms boost. There was one time where I -as Viktor- Flashed forward to ult a fleeing enemy Kalista. I got earen by Tahm mid-Flash and couldn't get out in time to get to the Kalista before she hopped away. Another time I was Vel'Koz and the two of us were defending a low-health tower from three mid-health enemies. Just as I began casting my ult, Tahm ate me and started retreating. "They were going to tower-dive us. I saved you!" "Yes, their dive was part of the plan! They were all lined up under our tower! I could have killed them all."
I don't think he's normally a bad player, but when his 'plays' affect our allies' positioning and our ability to execute our own strategies, it rarely ends well. I and another friend have tried to convince him that Tahm really doesn't fit our standard team-comp, but he's convinced that Tahm is OP. I'm not denying that he's strong, in fact his damage is ridiculous for how tanky he is, but his kit is incredibly annoying for his allies.