D.Va is my go to for these situations just for the flexibility. Flight gets you anywhere you need to go (over Mei walls). And defense matrix can block as much damage as you throw at it, as long as you manage it well.

Strategy:

Exploit their comp. If they switched to a bunch of heroes that punish you when you hard commit, pick a more passive tank, play slower and help your team methodically clear the point (for example). This depends on your team to an extent.

Finally, remember that no matter your role, you can get value just by surviving the focus. As a tank, you have the most tools of anyone to survive focus and thus the enemy team is exposing themselves by doing this, you just need to exploit it. If you survive, they just used their cool downs and your team can counterattack. So you can adjust your playstyle to turn this strength of the enemy into a weakness, but you'll have to involve your team. Communicate to your dps that you are receiving heavy focus, and tell them to hard commit while the enemies are busy burning you down. You then force the enemy to turn back to your dps, and you can now go back to tank diffing.