For some reason my units and defence buildings will only attack whatever is within view (not in the fog of war even with a radar) unless i manully tell them to attack. This plays hell with mid range artilery as i remember them been able to auto attack anything within range and not just the artilery but missile and advanced laser tower defences too have an attack range that for extends beyond view and into the fog of war but they will not auto attack and will sit there while an ai unit attacks it from the fog

Weapons won't shoot at radar blips unless you build (and enable) a targeting facility.

Guarding your structures at the edges of your base with scout planes also helps. It uses less energy, but your weapons will only shoot at what the scout planes can see. I use it in the beginning of the game when I don't have enough energy to run the targeting facility.

that seems kinda stupid but anyway im going through the campaign so i dont have eather targeting facility or aircraft available yet.

it just seems even more stupid that it doesnt affect the AI

It does affect the AI. What you're seeing is the AI doing the manual targeting for its units. Naturally, the AI is faster than we are so it looks like automatic targeting.

Another game I play, Warzone 2100, has the auto targeting stuff and that is sometimes a PITA, alerting the enemy units to my close presence before I'm ready to attack, or else by picking a target that it doesn't make sense to attack (ignoring threats to take out a building, etc,).

In the early missions that's an issue indeed. You'll have to be creative then. You can put some peewees/ak's on patrol in front of your base. They cost a bit more than an airplane and will probably be killed, but they'll warn you and keep the opponent busy for a short while.

I also don't put my heavy artillery in the front, so the short range defense provides line of sight. The short range defense will probably be shot down, but is easily replaced (and if you reclaim it first, it only costs a bit).

The AI does indeed shoot radar blips, but they only do what you can do manually. The difference is that humans tend to miss the blips, and the AI doesn't.

It seems to me that I tend to be better served by just building loads of units instead of static defense. Guardians and the like are cool, but a pile of Kbots or vehicles just seems to be more effective and flexible. I either go lots of build structures or a bunch of construction units guarding a few if space is an issue.