The poisons and curses right now aren’t even that crippling to the point where you must have a dispel for them. Other expansions had curses that would just flat up blow up a dps if you didn’t dispel it.
Also, the damage patterns on the bosses with poisons are not as brutal as the Worm boss was from Lair because the damage goes out for 10s, and then you have 20-30s to heal the group before the next round. It’s physically not possible to die if you use one defensive.