I agree that there´s no such thing as perfect balance, heck even in Warmachine (from what I have heard), you have to bring at least 2 or 3 lists in a serious tournament; because no single list can take everything your opponent can throw at you.
So you do your best to come up with lists you think can take most of what is out there.
Speaking of Privateer Press one thing they seem to do, that Games Workshop hasn´t done is actively participating in tournaments actually listening to their players.
Okay Asphyxious 2 is a little overpowered, okay we´ll scale him down a bit so he becomes more balanced.
Yes he´s still a nasty piece of work, and a lot of players groan when the see him, because they know they are in for a fight.
But he´s no invincible and neither is the army he´s in, there are ways for every army out there to defeat him.
GW on the other hand seems to close their ears, whenever the tournament players complain.
The problem with just one design team without serious feedback from the outside, is that while you might think your product is perfect and something makes perfect sense to you, that might not be so for an outsider.
A thing they could do is getting a hold of some people for the ETC and ask them to test out this draft to the new rules for an army and give their feedback on what they thought of it and what they might want to change.
Then take it into consideration, sure it might not give perfect balance, but I think it would be a hell of a lot better, then what we got now.
And as you said in the end that´s what most tournament players want a game that´s fairly well balanced.