I play all 6 tanks to some extent, mostly for M+, delves and open world content. My #1 frustration with Brewmaster is their self sustain is terrible compared to the other 5 tanks. I don’t see an easy fix for this because of how their mitigation mechanic, Stagger, works.
For those unfamiliar with Stagger, it basically converts around 70% of a direct damage into a 10 second DoT, so getting hit for 100K means you’re taking 30K directly, and the remaining 70K over 10 seconds. New hits will simply refresh/add to the dot ticks. To combat this Brewmaster can cleanse 50% of their current dot, but the ability has 2 charges on a 20 sec cooldown, so you can’t just mindlessly cleanse yourself.
Now if you have a healer, stagger is great because while your damage intake is high, it’s also very predictable. If the dot isn’t ticking too hard, it can simply be outhealed and you can save your cleansing for when it becomes larger. In M+ this can still be an issue if you’re taking a lot of damage, and there are mechanics that also require a lot of group healing.
But if you are soloing, the stagger mechanic becomes a weakness instead. As I said before, you can’t spam cleanse yourself which means you’re constantly taking way more damage than any other tank. The other 5 tank specs either stop a big portion up front with high armor, shield block, etc, or they heal it back up later.
You do have some self healing as a Brewmaster, but it’s not as reliable due to a big rng component. This means that you’re constantly taking dot ticks from stagger on top of any new incoming damage. If the incoming damage is mostly melee hits, you can survive fairly well because Brewmaster has very high dodge chance.
However taking any magic damage or bleeds will quickly overwhelm you.
TL;DR: Brewmaster is much weaker than the other 5 tanks for any solo content, and they generally require the most external healing to survive.
Now with that being said, I’ve been able to do T8 delves just fine as a 560ilv Brewmaster, but it requires way more effort and attention than my other tanks. You need to have Brann as a healer, and constantly check where he throws his potions.
I also find the dmg rotation for Brewmaster incredibly smooth and engaging. Unlike the other tanking specs, you don’t need a ton of haste to have a smooth experience (in fact, it’s your lowest prio stat).