With the recent fixes to Expose, there’s been a lot of talk about what Expose actually does.
When a character with an exposed debuff takes damage, they also lose 20% of their maximum health. Characters like Kylo Ren, who resist percantage based damage, along with Raid bosses, take a lower amount (0.04%) of damage.
The damage from Expose can’t be increased, nor can it be decreased or avoided – unless the debuff is resisted in the first place or cleansed.
Because it’s a garunteed, large amount of damage, a team which can inflict a lot of Expose debuffs can quickly destroy teams with no way to counter it.