>>543613676
>>543613457
The ballista switch becomes active after a set amount of time, it's unrelated to the dot
The dots affect the % bar that's below boss HP, once it goes down to 0 there's a bluish wave and the boss gets a yellow debuff stack, the gauge then fills back up (when it's recovering it's grey and the boss temporarily takes more crit damage)
Ideally you want 3 (max) of those yellow debuff stacks before you activate the ballista but 2 should also be fine if you're not pushing high floors. Activating the ballista removes the stacks and permanently debuffs the boss so that he he's more squishy.
Generally the boss should have dots active as much as possible (doesnt matter mechanics-wise during last phase) and you should focus on dealing damage during ballista activation + grey % gauge + the final phase, outside of those windows try to do whatever you need to survive
additional tip - if your students are dying from missiles, summon cover to absorb some and check whether they're standing too close to each other. Also some of Chokmah's skills straight up remove cover so you gotta time things right