Ok, so I have been thinking and thinking on this one: Why is it that I feel somewhat sorry for Dennis, yet the ass Aaron totally makes my skin crawl?
Then, it came to me in the two characters we tend to overlook... Valentine and Chey.
Valentine is totally devoted to Dennis, just as he is to her. And, it was his affectionate love for her that won me over to his having redemption possibilities... and I believe this is what made Owen rethink Dennis so much as he has.
On the other hand, you have Chey who loves Luke, yet despises the very existance of Aaron. Aaron shows the same aggressive behavior as Dennis with Rory (though not in a fighting manner), and he even tries to make up with Chey. But, Chey still does not like him. I think that fact, along with what I see as abusive behavior of Rory, makes me think he will prove to be a true ass in the end, not possessing the redemption qualities I find in Dennis.
So, that is my present theory: The animal characters in the stories will prove to be the one's who have the best judgement as to the nature of the other characters. And, in that regard, I believe Dennis will prove to be worth helping while Aaron will turn out to be the backstabbing, manipulative ass that Luke says he is.
Love and Peace,
Solace