Maintenance for the week of April 20:
• NA megaservers for patch maintenance – April 20, 3:00AM EDT (7:00 UTC) - 12:00PM EDT (16:00 UTC)
• EU megaservers for patch maintenance – April 20, 7:00 UTC (3:00AM EDT) - 17:00 UTC (12:00PM EDT)
Brawler creates a shield depending on how many enemies you hit with it, but does the shield keep increasing as you recast Brawler or does it just refresh the shield with a new cast?
Any consecutive cast of Brawler does not add a new shield until the previous shield has dissipated.
So my advice is to time and aim it well to get the most shield-points every time you use it.