Wild fluctuations? Really? I don't think you really understand polling.
But, let's assume you know what you're talking about and that polls shouldn't be used. What's the criteria then?
Yes, I understand polling quite well. I know its limits.
Polls are one element and human judgement is another. For example, Bernier might get some leeway for being a familiar face and name, as he came very close to potentially being Prime Minister.
Polls can't tell you how that will influence people on election day, especially if Scheer keeps shooting himself in the foot and a Trudeau scandal arises.
Polls can only tell you what's influencing people right now.