Hang on, aren't we talking about plausibility here? As in, how well what's presented to us in fiction matches up with reality?
In which case, this
Doesn't appear ineffectual.
Maggie wins, and is apparently good at the job.
is nonsense. You are arguing that Maggie is plausible because in the story she is 'effectual.' Well, of course the writer is going to make Maggie 'effectual' - it would be problematic to his own story if he wrote her any other way.
Your line of reasoning is like arguing faster-than-light spaceships are plausible because there's one called the Nostromo that travels faster than light. (We all understand the difference between fiction and reality, don't we?)
What might be more useful is to take a more specialised definition of 'plausible' in which we examine how well a story invention fits in with the rest of the story-world.
For example, a spider man that can walk on walls is not plausible in a story-world like, say, that which exists in a Merchant Ivory film; but would be completely plausible in a story-world in which radioactive spider-bites confer superpowers rather than radiation sickness, and goblin men hurl pumpkin bombs at people.
So are android sniffer dogs at all in keeping with the rest of the Alien 'verse, as we know it?
Ronoc makes a good point when he says that in the real world mechanised tractors have displaced draught horses and snowmobiles have displaced husky dogs. Like it or not, these are facts. But putting the real world aside for the moment; in the Alien 'verse that we all know and love can we imagine that elsewhere on Planet LV-492 colonial farmers are tilling their fields with ploughs pulled by android-horses, and perhaps closer to the poles other colonists are crossing snowy terrain not on snowmobiles but on android-husky drawn sleds?
Well, everyone can decide this answer for him or herself, but for me the notion seems rather odd.
I would certainly have scratched my head and wondered WTF if the Jarden family had hitched a horse-drawn wagon up to a team of android horses before pulling out of Hadley's Hope on the way to the derelict.