There is no doubt in my mind that the ATR has a critical engine. However, I don't really see the logic in designing one power lever to be larger than the other as a reminder.
Someone pointed out that there is no perceptible difference in control forces required to handle an engine failure on takeoff. While I've never had one in the airplane, I've had many 'V1 cuts' in the simulator and I've trained dozens of pilots to deal with them, and I agree with that observation. None of my students ever remarked on any differences in control forces required in this scenario, and I imagine that only an experienced engineering test pilot would be able to readily perceive any difference. Besides, in that scenario, a pilot must reflexively and promptly input what is required to keep the airplane from departing controlled flight. It is unlikely that a tactile reminder of which engine is critical would be useful; for him/her, the one that failed is now the critical engine in any case!
I would also go as far as to say that knowledge of the critical engine (and its application) is a double-edged sword. Pilots should know that even in modern airplanes, differences in required control pressures MIGHT exist depending on which engine fails. However, in the US the FAA also dictates that applicants must demonstrate handling a failure of the critical engine during a check ride. So an applicant taking a check ride might not know when an engine will fail, but he will know which one will fail. Since identifying the failed engine is of some importance, the evaluation of this skill is compromised by the FAA's requirement.