I have used those Pololu drivers and found that they really can't handle much more than 1 amp without a heatsink and it's very difficult to attach any kind of effective heatsink to them
My makergear reprap kit uses these, and they do indeed get hot. I replaced the heat sinks provided with these: Enzotech MOS-C1 Heatsinks only - Newegg.com which helped some. Adding an old computer 80mm fan inproved things again. Most useful though was the advice from their forums which was to use the little pot on the driver board to bring the current way down.