RE: Oracle: A R100 sensor is going to be nearly useless. You need to pay attention to all of the range markers, not just the maximum one. The only things that'll pick up at anywhere near maximum range are big honking ships. If it gets to the point where you have multiple ships in the 5-10kton+ range inside Sol and you aren't detecting and engaging with your own fleet before they get anywhere near your populations... yeah. Granted, sensor tech is really volume-hungry at low TLs, but you're using PDCs. Just pump up the size as high as you can afford and set the resolution to something more useful. I use R16 for all of my anti-ship sensors, but that's just paranoia about a certain type of 800 ton thing. You can probably get away with R40 or so; that'll give you a nice, long maximum range with a large sensor while still ensuring that you have an advanced warning zone for small vessels.
RE: Guardian: Don't. Just, don't. AMMs are a high-cost investment even when your TL is high enough for them to be effective, but at this they're nothing but a resource sink. There is literally nothing in the game that you will stop with 5 launchers throwing missiles with speeds and intercept chances like that. You're better off pushing hard for better tech, putting your resources into meson PD, putting resources into more ASM launcher bases, or some combination of those.
I'll put it another way: a TL4-5ish fleet with 3 AMM escorts might blow through a few hundred AMMs intercepting launches from half a dozen enemy missile ships, and that's if the enemy has low ammo stores and the player is a cheapass who only uses two AMMs per target. That's with tech good enough that a decent percentage of those AMMs are intercepting targets; keep in mind, too, that they're going to have a
lot of AMM launchers, enough to assign 2-3 missiles to every enemy ASM at ideal ratios. At that level the cost of those missiles is barely enough to make them a viable option. At TL1-2, you're frankly better off just teching up and hoping nothing nasty happens across you, because nothing you build will be particularly effective, but certain things like AMMs might actually make it worse by consuming minerals that you could have used for slightly more effective weapons now or much more effective weapons a few decades down the line.
But that's just, like, my opinion, man.
RE: Lasher: It's about the best you could hope for at this TL, but with ammo reserves and to-hit chances that low, you're not going to do much of anything unless you build hundreds of the things.
tl;dr: Really low tech weapons are a waste of time and resources. They won't pose a serious threat to anything that might stumble across you, and as long as Invaders are off it's highly unlikely that that will happen anyways. I honestly can't recall ever having NPRs or other special things show up in Sol, at least not for the first 50-60 years. Now, some of those 1m population "hidden last colony" scenarios starting in other systems with multiple habitable worlds... hoo boy. :x