BIS lists are mostly irrelevant unless you are full clearing on heroic farm for weeks. Understand stat priorities and decide if pieces are upgrades on an individual basis. Our 2 piece is amazing and our 4 piece is great so you do want to make sure to get and keep those.
Sorry but if you feel like a detriment there are probably a lot of things you can improve upon and I don't think it's a problem with the class. Brewmasters are fantastic tanks with high dps and good raid utility through Black Ox Statue raid shielding.
Keeping Shuffle up while tanking is mandatory, it's a given as a Monk. The skill is using Elusive Brew effectively, timing Guard for big hits, having good reaction time to Expel Harm or picking up Gift of the Ox orbs and using cooldowns effectively. You need to provide logs and your armory or it's hard for us to give specific advice. What fights do you struggle on? What parts?
Just saying generally "you feel like a detriment" is understandable if you are having trouble and frustrated, but if you want help we need details.