From the official post:
The brewmaster is a quirky character, though dangerous when underestimated. Brewmasters may seem to struggle with balance as they chug their concoctions in the middle of a fight, but this unpredictable behavior is far from foolhardiness. Most opponents barely have time to process the erratic nature of the brewmaster’s fighting tactics before they find themselves laid low—possibly the result of a keg smash to the head. When an opponent actually manages to land an attack, it’s often unclear how much the brewmaster feels it . . . if at all.
The gameplay for Brewmasters hasn’t quite fit their archetypes to this point. Rather than being the tricky martial artists, staggering around with an evasiveness that frustrates their opponent while being a little squishy when taking an unmitigated blow, Brewmasters have been more focused around large absorption shields and clutch self-healing. Our new design approach is to get more gameplay depth out of their strong, thematic abilities. Instead of Chi as a resource, which had little depth for Brewmasters, we’re switching to charges on Brew abilities that other abilities still interact with.