definitely not normal, especially for a new 2015. This thing is Throttle-by-wire, meaning there is no direct linkage between the engine and the accelerator pedal. It's all electronic... You shouldn't be getting any feedback through the accelerator.
It's under warranty, so if you think the problem is reproducible (i.e. you can prove it to a mechanic) take it back to the dealership. I don't feel any vibration through the pedal in my 2014.
