Naturally all depending on how sensitive the laser warning sensor is but I'd doubt just aiming the laser just a few meters off target would render it null and void, would be enough scatter in the atmosphere to direct lots of energy right at the helicopter and it's sensor.
And while everyone keeps on going on about how poorly the Russians are going I bet there's lots of notes being taken down all across the globe in regards how tanks/mechanized units vs modern ATGM's and UAV's look in today's day and age. It's the first time we have seen fully modern ATGM's and UAV's take on tanks, doubt the US thunder run for Bagdad could have survived the armament available today.