I am fairly naive on the significance of Augustine and he seems to be a flashpoint these days between Orthodox online. If you have any more thoughts I would be happy to hear them. Fr. Seraphim seems to take the nuanced position that the extremities of Augustine's theology were errors in good faith but that the man was unassailably a model of pious repentance and that he should be held high for that rather than posthumously bullied for his errors. At the same time his theological errors when extended further seems to have held major sway on the Romans and Protestants and their heresies.
		
		
	 
I'm not sure I have much insight. I've only just recently considered the possibility that Augustine could be questioned on some of these things.  Augustine is such a mainstay for thought in the West it's hard to critique for someone coming from my point of view.
There are these unspoken pre-conceptual frames people operate with.  We rarely talk about them, or think about them, because we just assume it.  This is how it feels to me with Augustine's ideas.
Augustine was the one who thought of things being meritorious or demeritorious before God.  Seems straightforward enough but when it's systematized there ends up being a certain way of thinking.  Especially when linked up with original sin, which is what he did.  He proposed that the internal character of our act is always sinful, even when we obey the law and do good. 
And so, Augustine theorized there must be some sort of special "preceding" grace that corrects our good deeds as we do them.
In other words, Your deed is only good when you are put in a "state of grace".   This is the system the Catholics work with.  
So, from here on out, we are working within a system of merits and demerits.  And people start thinking in systematic terms of transferring merits.  Rome essentially came up with this system where the Church has a treasury of merits, stored up by the Saints, which only it can dispense, to put you in a state of grace.  The people who became Protestants flipped out about this because you can kind of see how this totally takes the meaning and heart out of the whole situation and makes it look like God is running some strange factory.  You can also see how this is ripe for abuse, ie indulgences (selling merits on behalf of the dead) 
But, protestants were not able to see around Augustine at this point and still thought heavily of the whole situation as a transfer of merits from Christ to us.  Put your faith in Christ, merits are transferred.  This kind of description can be found in scripture but we've really latched onto the merit/demerit thing in the West. 
What you say about Seraphim Rose's nuanced approach is also something that we in the West do less of.  We generally think if we can study something (like the Bible) and get it just right (systematically understand it) then we'll be good.  We tend to trust the intellect over the heart.  We don't even have a good concept or definition of the heart.  Some people would think it just means emotion.
Anyways, I'm pretty sure this whole way of over-systemized thinking grew into the "I believe in the experts" and "I belive in science" people.  We trust smart people rather than seeking out and trusting holy people.