Yeah normally if it were a summoner in frontline doing 200k dmg I'd be like so what. The dots are much more easily handled and healed through because of the presence of more healers usually. But in feast there is only the one heal and if you keep on dishing out party wide dmg like that you will severely tax the opponent healer who is probably already under pressure by tank and/or melee and cause them to expend massive amounts of resources to try to keep the party alive nevermind topped off. This is an especially nightmarish scenario for Noct ast heals. Even if the dots don't outright kill the opponents the pressure on and expenditure of resources by the healer to keep party up will inevitably lead to a death as bursting someone becomes easier under those circumstances.