Mei is fundamentally stronger than a lot of heroes due to her bulk.
She has a lot of health with Ice block + Wall, sustained damage with freeze + RMB,
And self healing.
BUT WAIT, we arent done yet!!
She also has the ability to do huge damage long range (comparible to mcree),
She also has a massive area denial too with her primary AND her ult,
She can go invulnerable to ride out ults, cancel cc, block team mates.
Plus mei’s wall can protect her entire team, isolate enemies, be used for mobilty, etc.
And hey look at that, mei is a tank hybrid too.