Improved Disarm gives a +2 bonus to disarm attempts, but is that still added when you use the critical confirmation roll for Disarming Strike?
It probably sounds like a silly question I know, but I like to have clarity rather than assuming.
Short answer: No.
Long answer: The improved disarm feat provides a +2 to any disarm combat maneuver action you take. Disarming Strike is not a disarm combat maneuver, it simply borrows the rules from disarm for when you have successfully rolled a confirmation > target CMD.