A better time to remove it is JUST after it focuses. Of course, that might mean that it had a chance to do some damage.There's no action window between focusing and doing the damage. If the unit has no damage icons and is hoping for unopposed, you're right.
One great combo is Icetromper and a unit with a tactics icon. Then you can remove and damage with the Icetromper and then keep the opponent out for the remainder of the turn with the tactics.