Although, I love shaman tanking your comment need to be qualified.
A shaman tank who is well geared and going against a boss who is on farm will come close and in a few special scenarios surpass a warrior.
This is simply false. Mana is a manageable thing. Judging by your willingness to barely admit that they can tank dungeons, I’d assume you don’t know much about shaman tanking. Since even a hunter, boomkin, etc… can tank dungeons.
Who told you this? On the contrary many people (even noobs) have cleared MC. If you’re interested there’s a whole Shaman Tanking Discord server dedicated to help people.