Maeve is the lady of winter a millennia old elemental force, a focus of a large chunk of the raw power of a season her full power is incredible we just haven't seen it used properly. The loup garou is unstoppable you could nuke it and it would come out unscathed it was created by a divinely powerful curse. Not to mention Harry Dresden who is the focus of the DV world, he is fawned over by creature of 'godlike' power from across the spectrum from Heaven to Hell to elsewhere and beyond and he seems to has access to as much power as the plot demands. Are you really saying these three characters don't count out as plot devices (narrative tools)?
I think we may not all be on the same page where it comes to the term "Plot Device".
Ways & Means seems to define it as "any character that a large plot or series of plots can revolve around,, due to their power, motivation, or reputation."
But I think Silverblaze may be defining it as, "Any character, item, or location of such overwhelming power and/or position that a GM must make judgement calls about their actions such as to convey such power without causing player de-emphasis."
They are very close in concept, but of Ways' examples, I would only count Maeve as approaching the level of plot device, although technically Aurora, of similar power, was taken out by a small swarm of Pixies with boxcutters.
The second definition might be better named "
Total Plot Device" do differentiate the two meanings of the phrase.