You can wait for the pre-patch and level a Brewmaster Monk, otherwise I’d honestly suggest a Blood Death Knight because from what I’ve heard they’re the tank that’s least reliant on vengence stacks for damage.
Not sure if Blood DK’s can solo dungeons but I know for a fact that Brewmaster Monks can and I think Blood DK’s and Brewmasters are considered the best tanks in MoP. Not sure how true that is but I think I recall hearing that.
All tanks are viable in Pandaria, certainly moreso than past expansions, but Brewmaster and Blood will be the kings
Warrior: The least room for error. It’s not in nearly such a bad spot that you have to sweat just to be decent (Cataclysm…) but with a lack of self healing or active mitigation it does require a bit more effort than the others to be able to stand side by side with them
Druid: Plays kind of like Warrior but has much better personal tools that make it more forgiving and more valuable to the raid
Paladin: Brain off easy mode
Death Knight: Brain off easy mode but you also ran the healer out of a job
Monk: Most room for skill expression. The difference between a good Brewmaster and a mediocre Brewmaster is palpable. If you can play it well, you’ll be a god among men, but if you play it poorly you should probably look at the other classes
Overall no tank is super galaxy brain complex, so don’t be afraid to try any or all of them and see what sticks with you personally. Even one of the “more difficult” ones might just click with you in a way the easy ones don’t