I actually think Voyager needed a character like Q a lot more than TNG did. Voyager needed a recurring villain that they could meet up with every now and then even though their main goal was to travel as fast as possible back home. Q could have done that, while tempting them with instant transport home if only they'd sufficiently prove their humanity out in the oh so dangerous delta quadrant. That might still qualify him as a dumb plot device, but it would have made a little more sense.
Instead, Voyager kept meeting with the same dumb villains over and over again even though they should have fled their territory after three episodes, and killed off potentially interesting shipboard recurring characters, like Brad Dourif's psychopath crewman.