Part of what helped him was the really thin armor; they're not going to be able to take... anything, really. And the missiles are good, but with range that limited you're going to have to get really close to nasty things. That said, that's pretty much what you're shooting for at TL3ish.
RE: the Shield: Ditch the CIWS and add some more gauss turrets. CIWS only defends against missiles targeted at the ship it's mounted on, and functionally it behaves like a prepackaged gauss PD system.
One thing to seriously consider would be rushing to Box Launcher tech (via the missile launcher size/reload speed techs, which are worthwhile in and of themselves). From the look of things your launchers have no size reduction at all. Basically there is very little downside to using size-reduced launchers because of the way Aurora handles missile engagements: the size of each individual volley is what matters, as opposed to the weight of sustained fire you can throw. Firing 12 missiles per ship every minute will, on average, see more hits than 6 per ship every 30 seconds, at least if they have any sort of PD.
So, ferex, 0.5 size reduction would let you double your volley size without any increase in tonnage.
Box launchers are another nice little bit of tech, especially for lower-tech ships, because they can give you a seriously nasty alpha strike capability in exchange for very little volume; my typical design for my little 4-5k ton glass cannon frigates that I like to use at that TL includes a set of box launchers that can double the size of one volley.
But yeah, anyhow: they're basically sound designs, and after that it's mostly a matter of optimization vs. flavor vs. personal preference.