Best weapon type or skill tree for mid-game boss with rapid multi-phase attacks

[Madison66]

I'm stuck on the mid-game boss in the new action RPG that uses a rapid, multi-phase attack pattern I can't seem to dodge consistently. I've looked up general tips, but most guides are either too vague or focus on end-game builds I don't have access to yet. For players who have mastered this fight, what specific weapon type or skill tree provided the most effective balance of damage and mobility, and is there a particular tell or environmental cue I should watch for to anticipate the boss's most punishing area-of-effect attack?