@Nersius Bo/Br is really just not a good combo. Bo/Hu is the best choice for that mix of unconditional damage multipliers and survivability, while Bo/Su requires a bit more upkeep since you need to be applying Summoner's Mark to get the most damage out of it; I am personally a fan of Bo/Fi and Fi/Bo at the level we are at since you can easily proc the Chaser Skills with Jet Boots and get a very high Critical Rate, but it is squishier.
Though you do want to get all your classes to lv75 for the full Class Bonus bases stats (60HP, 10PP, 120 All-Pwr, 60 DEX, 90 All-Def), using a combo like Bo/Br in end-game UQ content is just not going to be an enjoyable experience.