Kind of. Right problem, different solution. We're going to err in the player's favor here, and make HealthPercentAfterDamage based on the same Damage amount as the left part of the equation is (ie, the full damage of the hit, before absorbs, before stagger, instead of after stagger).
OLD: (0.75 * Damage / MaxHealth) * (3 - 2 * (CurrentHealth - (Damage - Stagger)) / MaxHealth)
NEW: (0.75 * Damage / MaxHealth) * (3 - 2 * (CurrentHealth - Damage) / MaxHealth)
That will ensure that ISB doesn't reduce the chance to generate an orb on any given attack (but still will on the next attack by virtue of being higher health).