Thanks for the links.
I intentionally left my post vague, it was not due to lack of knowledge of the basic fundamentals of game design or theory. I did not want to sway my general inquiry by focusing the answers around specific details. I'm strictly prototyping at the moment, I'm not looking for polish. I should have specified that.
As a bit of background, I've actually worked on about two dozen games over the last 6 years, from a design/production standpoint. I'm well aware of the flow of implementing AI into a conventional game. It might surprise you to know that our AI programmers almost never actually launched the game or level environments. Most of their code work was performed in a simple cube environment with very few static meshes. I've never seen AI done at the end of a games lifecycle; although, I imagine each studio has their own approach. I'm only speaking from the perspective of 4 studios I've been involved with.
Minor tweaks to fake intelligence happen throughout the project, it's largely trial and error. You don't implement AI at the end of a project, it is the most time consuming aspect of most projects. You want your design and test team working with functional AI behaviour from the earliest point you can establish. In fact, most of the level design workflow was designed around the functionality of the AI; not the other way around.
I have to emphatically disagree with that Halo example. Making your enemies take more damage will end up making your enemies look dumb, not smarter. It is a horrible attempt to cover up how inadequate your AI is at self-preservation. Smarter AI should be able to survive in scenarios where they could die with a single shot. You should see games like Stalker or Killzone 2 (on hard difficulties), especially their tech demos. Another indicator of covering up bad AI is when you have different enemy types who have limited behaviour; instead of giving AI that can intelligently transfer between multiple behaviours. Quantity doesn't make up for lack of quality.
Most of the rules of traditional games fly out the window in a simplistic platformer, when you are limited to 100 events (I'm evaluating the engine for a personal project). A key reason why I never once used the word AI in my post, was because I'm not concerned with making them appear intelligent at the moment. I hope this post helps clear things up. I'm well aware of the direction of my intended project and have fleshed out exactly how I want my enemies to react in almost absurd detail; most of which is fairly out of the scope for my prototyping.
1) I was more concerned with how you would physically handle the act of having your enemies fire upwards or downwards. Would you pin their torso/arm and have them automatically face towards the player? Is a better solution to have animations for each enemy where they face upwards or downwards? My question was more centered around handling the sprite, not so much the reasoning behind why they are facing the user. Although, I'd gladly take advice behind engine tips for that as well.
2) As for the second question, the "for each" answer was what I was looking to find out about. I didn't know the engine had the ability to specify it that easily.
Thanks again!