What do you see as their weakness?
They are a better team than England and probably equal to or better than NZ because of having about equal forward pack and better outside backs. Maybe they will get smashed by Australia, but on paper they're as good as any of the other teams.
You get three hitups every set from To'o, May and sualii, as good as any team has ever fielded in terms of backs making metres up the middle, you have premier props in Paulo and papalii, you have class of luai controlling attack and an attacking brand of football emphasising 2nd phase play that troubled Australia when they played NZ. A more disciplined effort today and Samoa would have won comfortably, they were by far the better side. Their only weakness is at half and hooker, and their players there aren't massive liabilities.
Sure, Australia is the best team in this world cup, but Samoa are no flukes in this final and are as good a challenge as any other. Australia will win if their defensive line can control Samoan ruck speed and if their more mobile forwards play off each other through the middle targetting halfback-centre space of the Samoans. But I can also see Samoas dynamic forward pack opening the game up for luai to create magic.
It would be the culmination of taumalolo's brave decision to join Tonga if that comes off. I don't see why you are dismissing Samoa.