Okay I've completely forgotten about the AI driving in halo 3 and completely agree that it was god awful and should have mentioned it however I disagree with everything else you said, I have no idea where you got the 75% of them missing their shots from unless your playing on normal or easy because difficulty those effect their performance. Give a marine a spartan laser on heroic or legendary and he will almost never miss unless they just manage to go behind cover, you can definitely see this during the covenant mission and after destroying the anti air wraith a pelican comes with a Warhog and mongoose give one of the marines a spartan later since you start with one and watch him blow destroy everything. The halo 4 AI (the friendly ones) were really bad compared halo 3 they fwere less combat efficient like they shot 2 DMR round then they wait 2 sec then fire again..... Yea that might kill what a grunt, actually no the grunt will kill the marine first because at least they know how to use their weapons and throw grenades. The Spartan IV were just a little better like I said already in my previous post they have better reaction time compared to the marines but still pretty bad. These were experiences I've had that happen most of the time when I played these games. Oh and I probably should have just said three and two, when I mentioned previous titles, halo combat evolved AI were bad
Oh and I'm sorry for my English :/