Alternatively: we know that for Yellow at least, all the good bonuses came from Cultivation arts and base cultivation - which we have sewn up. Art mastery gave relatively little. We also know that Meizhen - the little overachiever that she is - only bothered to master 4 of her arts before breakthrough.With that aside, I once again believe that reaffirming our base cultivation to its greatest possible result would result in very powerful bonii upon breakthrough just like the Argent Soul Cultivation did when we broke through to yellow.
This, in general, suggests that art mastery isn't a huge part of our bonuses. Now, would mastering all 4 argent arts probably give us some kind of mastery bonus? Probably. Would it be anything close to what Argent Soul gave us (a cultivation art specifically focussed on giving massive foundation bonuses)? Most likely not.
Is there any real reason to think that combat argent art mastery is any better than, say, darkness mastery? Not really. The argent combat arts give a nice generic well rounded combat suite. There's no reason to think that they give any special bonuses to cultivation beyond what mastering good quality arts gives you.