If Heimer isn't going turrets as his primary, he's screwing himself over by denying himself early game farm. Dealing with missile harass is no big thing, especially if you have teleport. You can take as many missiles as you need to, then pill back, get full health, buy a few more health potions, and teleport back all without missing any exp at all.
If he is going turrets as his primary, there are a half dozen simple counters. Veigar, Sivir, Nidalee, Annie, Ashe, Twitch, and a lot of other common solo mids can all annihilate heimer turrets quite efficiently (though twitch usually pops his ult before trying large groups of them).