I think, in my own opinion, the answer to your question is that we as players wield far too much power. The amount of moaning whining and gripes on the threads about this fleet or that fleet, the balance of one ship against another just leads to constant revisions and updates to prove that mongoose is in touch with its customer base. I think Armageddon and the recent release of the Drakh minatures and then the Armageddon miniatures go to show that the customer base is loyal enough regardless of the mistakes made, it isn't necessary to pander to the whim of every megalomaniac with acess to the internet. Personally I don't think that is necesarily a good thing. Look at the rules for fighters which have swung backwards and fowards since the initial rules as a case in point.
You cannot satisfy all of the people all of the time and I believe it to be a mistake to attempt to satisfy the whines and gripes of those that shout loudest and most often from these threads. The gripes often only serve the need of a particular fleet or are an attemp to water down the hard hitters of others.
I think most people are of the opinion that the playtesters didn't do all that they could to thoroughly test Armageddon, but then the rest of us do not know what was submitted by them and rejected or the terms of the playtest they undertook, without knowing that, too much critiscism of them is a little unfair.
I would agree that 5 is insufficient to playtest a system, if you want it played and tested to death open it up to everybody but structure and support the playtesting with stats and results and forms to fill in and send back that are generic and of use to those who will be writing the rules and producing the stats, at least that way everyone has a say and everyone is in on it from the start.
Or do it in secret without the really annoying little hints in dribs and drabs from playtesters with the "i know something you don't know but can't tell you and it's so so cool" syndrome. Nor do I think playtesters should be selected by committee or by common vote. Mongoose use the PM system and ask those you would like to play test for you, just make sure you are asking them for the right reasons, or that they are saying yes for the right reasons, I'm certain you would not be short of volunteers.
Decision by committee is fine if you want no accountability, no responsibility, and a large amount of hot air.