It's been said, and I agree with, that Aggression doesn't very much impact CPU play calling. I know I've seen teams even with these lower aggressions on offense still go deep with frequency if my stupid safeties get burned or I call the wrong zone and the QB gets protection.
I really think it's either the playbook of the team itself or maybe something else internally that determines this. It's not even traced to slider sets (used to be that QB Acc was what made teams go deep, but having a set with CPU QB Acc at 70, 60, and 27 - and all go deep, I can agree with that having limited/no impact as well).
No more than they (overly) blitz as it is, imo. I've noticed the AI will blitz if I can't beat it, or it creates hurries/pressure. If I start beating it, it backs off...some. Often times, the next drive, I'll get a bit softer coverage. I usually run when I see this since they aren't attacking gaps. That usually gets them coming at me again, so then I try to beat the blitz with high percentage throws to try to get them back (or they risk letting me nickle-and-dime them up and down the field, as Collinsworth would say). Again, I think it's the playbooks as well as the flow of the game (what's working/what's not) as much as anything else.
Aggression for both offense and defense is mostly about speed of play development. How much effort/speed guys get to where they want to (or think they need to) be. And even that might not be too sharp as the offenses aren't terribly slow or whatever on these lower aggressions - maybe only on certain plays does it show up a lot (like sweeps, tosses, pulling/trap blocking, screens - maybe)
Offensive Aggression DOES have a sizable impact on sim stats, especially in yards per carry. EccentricMeat saw this and I can confirm that lower aggression did help the sim teams get better yards per carry. That's the main reason for the Offensive Aggression I have set.
It tends to occupy blockers because the DT has a larger range to where he can "pull" a blocker into an engagement instead of moving to the next level or sliding (the football term not the graphical Madden meaning) to pick up a blitzer or a defender coming in to make a play.
This is my way of trying to simulate double team concepts and the DL main role of creating defensive gaps instead of always trying to get penetration themselves. The high level block shedding DL can still penetrate. Ngata, Suh, Wilfork, those guys can still breakthrough, assuming sliders allow it, but they also will do the above even if they can't penetrate. The other defenders are more to exploit gaps (LBs, Ss) or operate more in open space (LBs, DBs) so these concepts are less important for them. You don't want a free runner trying to occupy a blocker when he can avoid engagement (hence why he's a free runner).
I find that my corners get in on run support pretty well. I use higher-than-most reaction sliders in my sets (based on what I see others using) so that might be why. I'm a big believer in the defense reacting with quickness and intensity and it should be player ratings/traits that make them act otherwise. Stanford Routt was almost the leading tackler in the game I played last night. They really react on outside runs for me.
I keep it on coverage since that's still the #1 responsibility of a CB. That's what he should be concerned with and I want that mindset in CB. If his AWR is bad, he'll still get beat, tricked, burned, either by route or by play action (I'm looking at you, Jimmy Smith!)
I use Balanced for the Strong Safety as that's the only DB I believe really has a split responsibility. He is to come up in run support (8th man in the box) as well as cover the TE or play a zone coverage. Many of them are also hard hitters, so I don't want that to go by the wayside either. For the FS and the CBs, if they are physical as well as can cover, I'll let their ratings determine that. Some don't do run support as well as others, whether it's a delayed reaction to the run or poor tackling. HB vs CB really is advantage: HB in a lot of cases, which is why a run support CB is praised as much as he is, or at least the run support skill is noted - because it's not terribly common on a CB.
That's my reasoning at least