Does Reprisal work on everything?

[Lodi]

Yup, it does. But since it's so short, it should be kept for tank/raid busters; it's not nearly as useful against mob packs as standard mitigation

[wereotter]

it's not nearly as useful against mob packs as standard mitigation

Since this was mentioned twice.... thought I'd add in that Arm's Length does work as a cooldown in this scenario (just in case you hadn't seen that it's different on tanks than on DPS) since it applies a slow debuff to enemies that hit you. Means you take less damage after popping it since they're attacking you more slowly.