Vuln stacks are a better option than damage downs. In well designed fights you can opt for melee uptime to have a bit more enrage buffer and eat a stack with the caveat that you need to mitigate a bit more next raidwide. Damage downs mean you have to solve the mechanic, usually in the intended way and instead lead to enrage being harder to meet if acquired. It provides the players semi meaningful choice instead of railroading into the timetable.