AO-Universe

How frequently are these AC's called on at the lower levels? I have a 24th level Advent, and I remember a disease attack once, maybe one chemical, and no radiation. I assume these come into play at some point, but I hate to waste too much AC on them now...

Really depends more on mob type than level I believe... but I'm too tired from work to really get into detail and I don't even know the specifics for sure so... :-X

I think Aliens do Radiation damage...

I'm a fr00b, so I don't have to worry about aliens.

Any other observations about mobs that do Chemical, Radiation or Disease damage would be appreciated.

Actualy, just because you're a Fr00b, doesn't stop you doing Alien raids...

You can't use the items, but you could either sell anything you win, or just be there helping your Org mates do a raid!

really it depends where you are. if you find 1 thing that hits you for rad dmg, theres probably more nearby that hit for the same dmg.
at lower level though, yes, melee and projectile are the most common. But the more you play / explore, the mob dmg types you will encounter.

You can do the city part of AI raids, but not the ship part.
Pretty much this is the gist of it.