All Bosses have an armor gauge. When their armor gauge is undamaged, Bosses will take lower damage. Use regular auto attacks versus in charge to harm their armor. When the armor is totally gone, in charge will take 30% more damage. You are now free to use all your abilities.

Many Bosses will use really heavy attacks versus you. When a Boss is about to launch a heavy attack, red signs will appear. Retreat from the significant zone as quick as possible. Use your incredibly elusive ability to move around much faster if you get into problem.