re: I rarely hear any news commentators addressing the complexity of the political situation there.
That's because no one knows anything. The situation changes daily. No one knows who most of the players are, and no one has the time or energy to invest in trying to figure it all out because it changes so much. It's not easy to break into a lot of the groups, especially if you don't know the language. And when you're relying on a contact to get you in, then you have to contend with the spin from that contact, the bribes, etc.
The people who do know what's going on have too much at stake/too much to do to blab. Decisions are made behind closed doors late at night. There's no upside to blabbing about it in the press the way there is here, espically if your intention is to destabilize/get more power for your group.
Moreover, the violence has many journalists largely confined to Baghdad. Kept in dark and fed shit comes to mind.
Here's something on what the increased violence means for journalists in Iraq
in this WP item.